CN112757344B - Robot interference shaft hole assembling method and device based on force position state mapping model - Google Patents
Robot interference shaft hole assembling method and device based on force position state mapping model Download PDFInfo
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Abstract
The application provides a robot interference shaft hole assembling method and device based on a force position state mapping model, and relates to the technical field of robot automatic assembling, wherein the method comprises the following steps: constructing a robot assembly system of the interference shaft hole; establishing a state mapping model of the relative pose of the shaft hole and the interaction force; acquiring a current interaction force through a force sensor signal in the robot assembly system; and obtaining the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of the system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller. Therefore, the assembly of the interference shaft hole is realized in a generalized admittance control mode by establishing a state mapping model of the relative pose and interaction force of the interference assembly of the shaft hole and using a robot power control technology.
Description
Technical Field
The application relates to the technical field of automatic robot assembly, in particular to a robot interference shaft hole assembly method and device based on a force position state mapping model.
Background
With the rapid development of robot technology, robots are increasingly used in various fields of the machine manufacturing industry. In the machine manufacturing industry, the assembly task is an indispensable ring. In order to meet the demand of assembly automation, the robot assembly technology becomes a research hotspot of the current technology. The shaft hole assembly is the most common and simplest task form in the mechanical manufacturing industry, and the research on the shaft hole assembly task of using the robot assembly technology to complete clearance fit is relatively mature, but the research on the shaft hole assembly task of using the robot assembly technology to complete interference fit is not complete.
Aiming at the problem of shaft hole assembly, one of the general technical paths is to detect an assembly mechanical signal through a force sensor and realize a shaft hole assembly task through a force control technology. The technical path based on force control solves the problem of shaft hole assembly by two methods: model-based methods and non-model-based methods. The model-based method comprises an active compliance control mechanism, a passive compliance mechanism and the like. In the related art, clearance shaft hole assembly is generally used as a research object, and both a model-based method and a non-model-based method are involved.
However, a precondition in the related art is that the shaft hole fitting property is the clearance fit. For the task of interference shaft hole assembly, the above method is not suitable due to the change of the fitting property of the shaft hole. After the shaft hole matching property changes, on one hand, the interactive mechanical model has substantial change, and the mechanical model built based on clearance fit is not applicable any more. On the other hand, the interference fit property greatly restricts the exploration freedom degree of the assembly process, so that the training process of reinforcement learning is difficult to perform. Therefore, a new force control method for solving the problem of interference shaft hole assembly is needed.
Disclosure of Invention
The present application is directed to solving, at least to some extent, one of the technical problems in the related art.
Therefore, a first objective of the present application is to provide a method for assembling an interference shaft hole of a robot based on a force position state mapping model, and provide a generalized admittance control method based on a model by establishing a force position state mapping model for interference shaft hole assembly, so as to complete an assembly task of the interference shaft hole.
The second purpose of the application is to provide a robot interference shaft hole assembling device based on a force position state mapping model.
In order to achieve the above object, an embodiment of the first aspect of the present application provides a method for assembling a robot interference shaft hole based on a force-position state mapping model, including:
constructing a robot assembly system of the interference shaft hole;
establishing a state mapping model of the relative pose of the shaft hole and the interaction force;
acquiring a current interaction force through a force sensor signal in the robot assembly system;
and acquiring the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of a system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller.
According to the robot interference shaft hole assembling method based on the force position state mapping model, a robot assembling system of the interference shaft hole is constructed; establishing a state mapping model of the relative pose of the shaft hole and the interaction force; acquiring a current interaction force through a force sensor signal in the robot assembly system; and obtaining the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of the system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller. Therefore, the assembly of the interference shaft hole is realized in a generalized admittance control mode by establishing a state mapping model of the relative pose and interaction force of the interference assembly of the shaft hole and using a robot power control technology.
Optionally, in an embodiment of the present application, the robot assembling system includes: the robot comprises a force sensor, a force sensor signal amplifier, a force sensor data acquisition card, a robot controller, a system controller, a circular hole, a circular shaft, a shaft holder and a hole holder; the fit property of the round hole and the round shaft is interference fit, and the robot assembly system for constructing the interference shaft hole comprises a circular hole and a circular shaft;
the robot base is fixed on the table top, the tail end of the robot is fixedly connected with the shaft holder, and the shaft holder holds a shaft to be assembled;
the lower end of the force sensor is fixedly connected with the table board, the upper end of the force sensor is fixedly connected with the hole clamp holder, and the hole clamp holder clamps a hole to be assembled;
the force sensor signal is uploaded to the system controller through the force sensor signal amplifier and the force sensor data acquisition card;
control instructions of the system controller are sent to the robot via the robot controller.
Optionally, in an embodiment of the present application, the establishing a state mapping model of the shaft hole relative pose and the interaction force includes:
in the state mapping model, the radius of the shaft is R, the inner radius of the hole matched with the shaft is R, the matching property is interference, and the outer radius of the hole is R1The depth of the hole is L, the origin of a hole coordinate system is defined at the center of the circle of the upper end surface of the hole, the X-axis direction is the same as the X-axis direction of the force sensor, the Y-axis direction is the same as the Y-axis direction of the force sensor, the Z-axis direction is the same as the Z-axis direction of the force sensor, and the Z-axis direction is also the axial direction of the hole;
integrating the contact area of the shaft and the hole to obtain an interaction force corresponding to the relative pose of the specific shaft hole;
acquiring detection data of a force sensor as force and moment applied to the center of the bottom end face of the hole, performing stress analysis by taking the hole as an object, integrating the stress of all contact positions by taking the center of the bottom end face of the hole as an equivalent point of analysis, and then equivalently obtaining force and moment acting on the center of the bottom end face of the hole, thereby acquiring an initial state mapping model of the relative pose of the shaft hole and the interaction force;
and simplifying the initial state mapping model to obtain the state mapping model.
Optionally, in an embodiment of the present application, pose control of the robot employs a dual closed-loop control framework, the robot performs position closed-loop, the robot performs force closed-loop under control of the generalized admittance controller;
the generalized admittance control rate is:
wherein x isrfrFor the reference pose of the axis in the assembly process,
is xrfrThe first derivative of (a) is,
is xrfrSecond derivative of, Md，Dd，KdIs a control parameter of the generalized admittance controller, A is a directional control matrix of the generalized admittance controller, xdA desired parameter for the output of the generalized admittance controller,
is xdThe first derivative of (a) is,
is xdSecond derivative of (F)extFor the equivalent force vector of the stress at the bottom of the hole end face, F, caused by deformation of the shaft hole during assemblyrfrAccording to the nominal size of the axle hole and according to the reference pose xrfrThe obtained reference force is calculated.
Optionally, in an embodiment of the present application, the method further includes:
and when the position of the hole is not horizontally placed or the hole is in a motion state, the current interaction force acquired by the force sensor signal is adjusted.
In order to achieve the above object, an embodiment of the second aspect of the present application provides a robot interference shaft hole assembling device based on a force position state mapping model, including:
the construction module is used for constructing a robot assembly system of the interference shaft hole;
the establishing module is used for establishing a state mapping model of the relative pose of the shaft hole and the interaction force;
the acquisition module is used for acquiring the current interaction force through a force sensor signal in the robot assembly system;
and the processing module is used for acquiring the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of the system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller.
The robot interference shaft hole assembling device based on the force position state mapping model comprises a robot assembling system for constructing interference shaft holes; establishing a state mapping model of the relative pose of the shaft hole and the interaction force; acquiring a current interaction force through a force sensor signal in the robot assembly system; and obtaining the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of the system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller. Therefore, the assembly of the interference shaft hole is realized in a generalized admittance control mode by establishing a state mapping model of the relative pose and interaction force of the interference assembly of the shaft hole and using a robot power control technology.
Optionally, in an embodiment of the present application, the robot assembling system includes: the robot comprises a force sensor, a force sensor signal amplifier, a force sensor data acquisition card, a robot controller, a system controller, a circular hole, a circular shaft, a shaft holder and a hole holder; the circular hole is in interference fit with the circular shaft; the building module is specifically configured to:
the robot base is fixed on the table top, the tail end of the robot is fixedly connected with the shaft holder, and the shaft holder holds a shaft to be assembled;
the lower end of the force sensor is fixedly connected with the table board, the upper end of the force sensor is fixedly connected with the hole clamp holder, and the hole clamp holder clamps a hole to be assembled;
the force sensor signal is uploaded to the system controller through the force sensor signal amplifier and the force sensor data acquisition card;
control instructions of the system controller are sent to the robot via the robot controller.
Optionally, in an embodiment of the present application, the establishing module is specifically configured to:
in the state mapping model, the radius of the shaft is R, the inner radius of the hole matched with the shaft is R, the matching property is interference, and the outer radius of the hole is R1The depth of the hole is L, the origin of the hole coordinate system is defined at the center of the circle of the upper end surface of the hole, and XThe axial direction is the same as the X-axis direction of the force sensor, the Y-axis direction is the same as the Y-axis direction of the force sensor, the Z-axis direction is the same as the Z-axis direction of the force sensor, and the Z-axis direction is also the axial direction of the hole;
integrating the contact area of the shaft and the hole to obtain an interaction force corresponding to the relative pose of the specific shaft hole;
acquiring detection data of a force sensor as force and moment applied to the center of the bottom end face of the hole, performing stress analysis by taking the hole as an object, integrating the stress of all contact positions by taking the center of the bottom end face of the hole as an equivalent point of analysis, and then equivalently obtaining force and moment acting on the center of the bottom end face of the hole, thereby acquiring an initial state mapping model of the relative pose of the shaft hole and the interaction force;
and simplifying the initial state mapping model to obtain the state mapping model.
Optionally, in an embodiment of the present application, pose control of the robot employs a dual closed-loop control framework, the robot performs position closed-loop, the robot performs force closed-loop under control of the generalized admittance controller;
the generalized admittance control rate is:
wherein x isrfrFor the reference pose of the axis in the assembly process,
is xrfrThe first derivative of (a) is,
is xrfrSecond derivative of, Md，Dd，KdIs a control parameter of the generalized admittance controller, A is a directional control matrix of the generalized admittance controller, xdA desired parameter for the output of the generalized admittance controller,
is xdThe first derivative of (a) is,
is xdSecond derivative of (F)extFor the equivalent force vector of the stress at the bottom of the hole end face, F, caused by deformation of the shaft hole during assemblyrfrAccording to the nominal size of the axle hole and according to the reference pose xrfrThe obtained reference force is calculated.
Optionally, in an embodiment of the present application, the apparatus further includes:
and the adjusting module is used for adjusting the current interaction force acquired by the force sensor signal when the position of the hole is not horizontally placed or when the hole is in a motion state.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic flowchart of a method for assembling an interference shaft hole of a robot based on a force-location state mapping model according to an embodiment of the present disclosure;
FIG. 2 is an exemplary diagram of a robotic assembly system for interference shaft holes in accordance with an embodiment of the present application;
FIG. 3 is a schematic view of an interference shaft hole assembly process according to an embodiment of the present application;
FIG. 4 is a schematic diagram illustrating the definition of independent parameters describing the relative pose of the shaft hole according to the embodiment of the present application;
FIG. 5 shows a horizontal declination of an embodiment of the present application
A schematic diagram of independent parameters describing the relative pose of the shaft hole in a plane;
FIG. 6 is a schematic view in the plane X-O-Y of the ds infinitesimal inner shaft hole assembly according to an embodiment of the present application;
FIG. 7 is a schematic diagram illustrating the division of the relative attitude status of the axial holes in the X-O-Y plane according to the embodiment of the present application;
FIG. 8 is a schematic diagram illustrating a corresponding relationship between a relative pose of an axial hole in an X-O-Y plane and an interaction force according to an embodiment of the present application;
FIG. 9 is a block diagram of system control for an interference shaft hole assembly according to an embodiment of the present application;
fig. 10 is a schematic structural diagram of a robot interference shaft hole assembling device based on a force position state mapping model according to an embodiment of the present application.
Detailed Description
Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application and should not be construed as limiting the present application.
The following describes a robot interference shaft hole assembling method and device based on a force position state mapping model according to an embodiment of the present application with reference to the accompanying drawings.
Fig. 1 is a schematic flowchart of a method for assembling an interference shaft hole of a robot based on a force-location state mapping model according to an embodiment of the present disclosure.
In particular, the difficulty of force-controlled assembly of interference shaft holes lies in the following two points. Firstly, the robot has ultrahigh control precision requirement. Any robot positioning accuracy error will cause assembly errors. The second is a highly uncertain task model. And the models related to the tasks such as elastic/plastic deformation, friction force, form and position errors and the like between the hole and the shaft are difficult to accurately establish. Due to the existence of uncertainty, it is difficult to establish a one-to-one correspondence between pose and force.
The method and the device realize the assembly of the interference shaft hole by establishing a state mapping model of the relative pose and the interaction force of the interference assembly of the shaft hole, using a robot power control technology and in a generalized admittance control mode.
As shown in fig. 1, the method for assembling the interference shaft hole of the robot based on the force position state mapping model comprises the following steps:
and 101, constructing a robot assembly system of the interference shaft hole.
In an embodiment of the present application, a robotic assembly system comprises: the robot comprises a force sensor, a force sensor signal amplifier, a force sensor data acquisition card, a robot controller, a system controller, a circular hole, a circular shaft, a shaft holder and a hole holder; the fit property of the round hole and the round shaft is interference fit, and the robot assembly system for the interference shaft hole is constructed and comprises; the robot base is fixed on the table top, the tail end of the robot is fixedly connected with the shaft holder, and the shaft holder holds a shaft to be assembled; the lower end of the force sensor is fixedly connected with the table top, the upper end of the force sensor is fixedly connected with the hole clamp holder, and the hole clamp holder clamps the hole to be assembled; uploading the signal of the force sensor to a system controller through a force sensor signal amplifier and a force sensor data acquisition card; control instructions of the system controller are sent to the robot via the robot controller.
For example, as shown in fig. 2, the construction of the interference shaft hole robot assembly system includes: the system comprises the following components: 1. the robot comprises a force sensor, a force sensor signal amplifier, a force sensor data acquisition card, a robot controller, a system controller, a circular hole, a circular shaft, a shaft holder and a hole holder, wherein the force sensor, the force sensor signal amplifier, the force sensor data acquisition card, the robot controller and the system controller are respectively arranged at the positions of the circular hole, the circular shaft, the shaft holder and the hole holder, and the circular hole and the circular shaft are in interference fit.
Specifically, as shown in fig. 2, the robot base is fixed on the table top, and the end of the machine is fixedly connected with a shaft holder, which holds the shaft to be assembled. The lower end of the force sensor is fixedly connected with the table board, the upper end of the force sensor is fixedly connected with the hole clamp holder, and the hole clamp holder clamps the hole to be assembled. The force sensor signal is uploaded to the system controller through a force sensor signal amplifier and a force sensor data acquisition card. The control instruction of the system controller is sent to the robot through the robot controller. The whole assembly process is completed by a robot. The generalized admittance control strategy of the whole assembly process is completed by the system controller.
And 102, establishing a state mapping model of the relative pose of the shaft hole and the interaction force.
In the embodiment of the present application, in the state mapping model, the radius of the shaft is R, the inner radius of the hole and the shaft fit is R, the fit property is interference, and the outer radius of the hole is R1The depth of the hole is L, the origin of a hole coordinate system is defined at the center of the circle of the upper end surface of the hole, the X-axis direction is the same as the X-axis direction of the force sensor, the Y-axis direction is the same as the Y-axis direction of the force sensor, the Z-axis direction is the same as the Z-axis direction of the force sensor, and the Z-axis direction is also the axial direction of the hole; integrating the contact area of the shaft and the hole to obtain an interaction force corresponding to the relative pose of the specific shaft hole; acquiring detection data of a force sensor as force and moment applied to the center of the bottom end face of the hole, performing stress analysis by taking the hole as an object, integrating the stress of all contact positions by taking the center of the bottom end face of the hole as an equivalent point of analysis, and then equivalently obtaining force and moment acting on the center of the bottom end face of the hole, thereby acquiring an initial state mapping model of the relative pose of the shaft hole and the interaction force; and simplifying the initial state mapping model to obtain the state mapping model.
Specifically, the first-mentioned state mapping model of the shaft hole relative pose and the interaction force is based on the following assumed conditions: 1) on the large-scale pose description, the axis and the hole are assumed to be rigid bodies, and on the small-scale deformation analysis, the axis and the hole are assumed to be flexible bodies; 2) the strain characteristics of the shaft and bore conform to the small strain assumption; 3) the stress characteristics conform to a linear elastic assumption; 4) the friction type in the assembling process is coulomb friction; 5) all shaft hole assembly deviations are small-scale changes; 6) only the shaft hole insertion stage is concerned, and processes such as search import and the like are not in the model description range.
Then, as shown in fig. 3, in the state mapping model of the relative pose and the interaction force of the shaft hole, the radius of the shaft is R, the inner radius of the fit between the hole and the shaft is R, the fit property is interference, and the outer radius of the hole is R1The depth of the hole is L. The origin of the hole coordinate system is defined at the center of a circle on the upper end surface of the hole, the X-axis direction of the hole coordinate system is the same as the X-axis direction of the force sensor, the Y-axis direction of the hole coordinate system is the same as the Y-axis direction of the force sensor, the Z-axis direction of the hole coordinate system is the same as the Z-axis direction of the force sensor, and the Z-axis direction is also the axial direction of the hole.
As shown in fig. 4, due to the waitingThe assembled round hole and the round shaft are symmetric objects around the center of the center line of each round hole and the center line of each round shaft, so that the relative pose of the shaft hole in a hole coordinate system can be expressed by 5 independent parameters. The 5 independent parameters used to describe the relative pose are as follows: 1) shaft center line vertical declination angle θ: expressed in the form of spherical coordinates, the included angle between the axis central line and the Z axis; 2) horizontal deflection angle phi of the shaft center line: expressed in a spherical coordinate mode, the included angle between the projection of the axis central line in an X-O-Y plane and the X axis; 3) shaft center line insertion depth l: the axial centerline length below the X-O-Y plane; 4) horizontal offset distance d between shaft center line and hole center line at insertion depth of l/2x: x coordinate value below the X-O-Y plane and at the position where the axial central line length is l/2; 5) horizontal offset distance d between shaft center line and hole center line at insertion depth of l/2y: and Y coordinate value below the X-O-Y plane and with axial central length of l/2.
As shown in FIG. 5, in order to more clearly show the expression of the relative pose of the shaft hole through the 5 independent parameters, the three-dimensional model is projected to the plane where the vertical deflection angle theta of the center line of the shaft is located, i.e. the X-O-Z plane of the hole coordinate system is turned by the horizontal deflection angle along the Z axis
The resulting flat surface. The vertical deflection angle theta of the shaft center line and the insertion depth l of the shaft center line are shown in FIG. 5, dxAnd dyIs embodied in the projection view as
Further, the assembly force of the shaft with the hole is derived from the deformation of the shaft-hole contact area during assembly. According to the micro-integration strategy, firstly, the contact deformation and the deformation stress are analyzed point by point, then integration is carried out in a contact area, the interaction force corresponding to the relative pose of a specific shaft hole is obtained, referring to fig. 5, firstly, under the condition that the central line of a specific shaft is inserted into a depth l, the whole contact space is differentiated according to the Z direction of a hole coordinate system, and each infinitesimal is recorded as ds.
Referring to FIG. 6, in the ds infinitesimal, the hole is a hollow cylinder, the axis is an elliptic cylinder, and the center of the hole is marked as OhThe center of the axis is marked as Op. Establishing a coordinate system X-O in the projected ds infinitesimal along the X-axis and Y-axis directions of the spatial mesopore coordinate systemh-y. The center O of the time axispIn x-Oh-expressed in the y coordinate system as:
where s represents the distance in the Z direction from the ds infinitesimal to the Z coordinate minimum position of the shaft bottom end face. According to the assumption that all the shaft hole assembly deviations are small-scale changes, the high-order small quantity is ignored, and the circle center O of the shaftpIn x-Oh-expressed in the y coordinate system as:
within the ds infinitesimal, the inner contour function of the pore is expressed as: x is the number of2+y2＝R2。
Within the ds infinitesimal, the outline function of the axis is expressed as: (x-O)px)2c2θ+(y-Opy)2＝r2. Wherein, OpxAnd OpyRepresenting the centre of a circle O of the shaftpIn x-Oh-abscissa and ordinate in the y-coordinate system.
Referring to fig. 6, a infinitesimal d α is divided within a ds infinitesimal. From OhStarting from the X axis, a ray is made along the direction of an included angle alpha with the X axis, and the ray intersects with the inner circle profile of the hole at a point F and intersects with the outer circle profile of the axis at a point G respectively. Is easy to know, OhF is equal to the bore inner profile radius, OhG is a function of the infinitesimal parameters (s, α) and is written as:
according to Lame's equalisation, the stress at point F at angle α is:
wherein E ish，EpModulus of elasticity, u, of the material of the bore and the shaft, respectivelyh，upRespectively the poisson's ratio of the material of the bore and the shaft.
To this end, the arbitrary contact position may be expressed by a infinitesimal parameter (s, α), i.e. the stress p of the arbitrary contact position is a function of the infinitesimal parameter (s, α).
Referring to fig. 6, a force sensor is disposed at the bottom end surface of the hole, and its detection data may be equivalent to a force and moment applied to the center of the bottom end surface of the hole. And (3) performing stress analysis by taking the hole as an object, taking the center of the bottom end face of the hole as an equivalent point of analysis, and integrating the stress of all the contact positions to be equivalent to force and moment acting on the center of the bottom end face of the hole:
where μ is the coefficient of friction between the shaft and the hole, H is the bottom layer thickness of the hole, and s and c represent sine and cosine functions. Alpha is alphalAnd alphauIs the lower and upper bounds, s, of the integral of the angle infinitesimal alphalAnd suIs the lower and upper bound on the integral of the length bins s:
recording the force generated by the assembly deformation of the shaft hole as a force vector Fext，Fext＝[Fx,Fy,Ff,Mx,My]T。
The force vector F is different because the stress at each position is different due to different relative pose parameters, and the deformation area is also differentextIs a function of the relative pose of the shaft bore. Recording as follows:
so far, a model of the interaction force of the relative pose of the shaft hole and the force sensor is preliminarily established.
Due to the influence of uncertainty, the actual relation between the relative pose of the shaft hole and the measurement result of the force sensor cannot be completely consistent with the model. When errors such as dimension errors and form and position errors occur in the shaft and the hole, the actual measurement of the force sensor has a large difference with the model calculation result. If only the inverse operation of the model is relied on as the only control basis, it may cause the system to diverge. Meanwhile, a large number of nonlinear links exist in the model, and analysis and calculation are difficult. Therefore, the model is simplified, the relative pose relationship between the shaft and the hole is judged by judging the relationship between the force signals, and the judgment accuracy and robustness are improved.
And decomposing the relative pose relation of the spatial axis and the hole into X-O-Z and Y-O-Z orthogonal planes for analysis.
Referring to FIG. 7, in the X-O-Z plane, the deviation angle of the hole centerline is denoted as θy，
Where t represents the tangent function, t-1Representing the arctan function.
The shaft hole relative poses can be classified into 9 types under a specific shaft center line insertion depth i. The corresponding state changes and parameters are as follows:
(θy＝0,dx＝0)→P0
(θy＝0,dx>0)→P1
(θy＝0,dx<0)→P-1
(θy>0,dx＝0)→D0
(θy>0,dx>0)→D1
(θy>0,dx<0)→D-1
when theta isy＝0，dxAt change, i.e. state change at P-1,P0,P1In one case, within each ds infinitesimal,
are equal. Then
When l is known, the signal is transmitted,
is a constant value. When d isx＝0，θyAt change, i.e. state change is in
P0,D0One of them, sl+ s and su-s is within the corresponding ds infinitesimal pair,
are opposite numbers. Then Fx＝0。
Refer to FIG. 8 in order
As an ordinate, to
As abscissa, P-1→P0→P1Corresponding to a slope of
The straight line of (a) is,
corresponds to a straight line coinciding with the longitudinal axis. According to the continuity of the relative pose state and the continuity of the interaction force, D1,D-1,
The states correspond to four regions divided by two straight lines.
In the Y-O-Z plane, the deviation angle of the hole center line is recorded as thetax，
The partition judgment method of the relative pose and the interaction force of the corresponding shaft hole is the same as that of the shaft hole.
The force position model has the advantages that the states of the shaft and the hole can be judged through the signals of the force sensor, the shaft hole assembling state does not need to be solved by using a position encoder and robot kinematics, and the judgment state is only based on the measurement result of the force sensor. Compared with a method for judging the relative pose state of the shaft and the hole through encoder feedback and kinematics of the robot, the method for judging the relative pose state of the shaft and the hole through the force sensor signal is more accurate; the force position model has the beneficial effects that when the shaft hole has form and position errors, the meaning corresponding relation of the relative pose relation of the shaft hole and the interactive acting force is changed. For the batch production task, the size of the shaft hole cannot be accurately obtained, so that the one-to-one correspondence relationship between the relative pose relationship of the shaft hole and the interaction force cannot be established. And the state of the shaft hole assembly is judged according to the force sensor signal, so that the method has stronger adaptability to the uncertainty of the shaft to be assembled and the hole, and even if the shaft hole has form and position errors, the partition state can not be changed, so that the judgment on the relative pose of the shaft hole is more accurate.
It should be noted that the model established in step S102 is a corresponding relationship between the relative pose of the axial hole and the interaction force, and the interaction force cannot be directly measured in practical application. In practical terms, a force sensor is mounted at the rear end of an object in the assembly shaft hole for estimating the interaction force of the assembly process.
An alternative (realizable) approach is to mount the force sensor at the bottom end of the hole. The force sensor can at least detect five-dimensional force signals including X-direction force, Y-direction force, Z-direction force, X-direction moment and Y-direction moment. The five-dimensional force signal measured by the force sensor is recorded as a force vector Fssr。
The force F generated by the assembly deformation of the shaft hole by taking the hole as a stress analysis objectextForce of the force sensor on the hole-FssrAnd other forces such as inertia force, coriolis force, gravity and the like applied to the hole are balanced,
wherein x ishThe pose of the center of the bottom end face of the hole, M the inertial matrix of the hole in its bottom end face, C the Coriolis force matrix of the hole in its bottom end face, hg the gravity matrix expressed in the hole coordinate system.
For a common state, the hole is horizontally placed in the space, and the position and posture of the hole are kept in a static state during the assembly process, the stress balance of the hole is expressed as:
wherein m ishIs the mass of the hole and g is the acceleration of gravity.
Therefore, the interaction force in the assembly process can be estimated according to the measurement data of the force sensor, the motion information of the hole and the inherent inertia parameter information, and the relative pose state of the shaft and the hole can be judged by combining the model established in the step S102. The force sensor signal filtering has the advantages that when the position of the hole is not horizontally placed or the hole is in a motion state, the force sensor measuring result caused by a mechanical signal except the shaft hole assembling force can be compensated through the compensation process, and further accurate state identification is guaranteed.
And 103, acquiring the current interaction force through a force sensor signal in the robot assembly system.
And 104, acquiring the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of the system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller.
Specifically, based on the state mapping model, a model-based generalized admittance controller is provided for completing an interference shaft hole assembly task.
Referring to fig. 9, in the control block diagram of the system, the pose control of the robot adopts a double closed-loop control framework, and the robot performs position closed-loop under the control of a classical PID controller. The robot performs a closed force loop under the control of the proposed generalized admittance controller. The generalized admittance control rate is as follows:
wherein x isrfrFor the reference pose of the axis during the assembly process: x is the number ofrfr＝[dx dy l θx θy]T。
Specifically, the axial centerline insertion depth/reference value is not 0, and all other four-dimensional reference parameters are 0. x is the number ofdIs a desired parameter of the generalized admittance controller output. FextThe stress caused by the deformation of the shaft hole during the assembly process is the equivalent force vector at the bottom of the end face of the hole. FrfrAccording to the nominal size of the axle hole and according to the reference pose xrfrIn general, the reference force obtained by calculation is not 0 only in the Z direction, and all other four-dimensional reference forces or reference moments are 0. The A matrix is a task information matrix of the generalized admittance controller and is used for determining the control direction of the expected pose output by the generalized admittance controller. Md，Dd，KdThe control parameters of the generalized admittance controller are used for determining the variation amplitude of the expected pose output by the generalized admittance controller.
In the generalized admittance control rate, the implementation method of the control direction is as follows:
referring to fig. 6 and 7, in the state mapping model of the shaft hole relative pose and the interaction force, when the shaft hole relative pose is in different states, the controller should have different control directions.
For dxAnd dyThe control direction is based on the following: when the shaft hole is in the state P1，D1，
When d is greater thanx>0，
When the shaft hole is in the state P-1，D-1，
When d is greater thanx<0，
Due to F in the assembly processzConstant positive, FxCan uniquely judge the positive and negative of dxPositive and negative. Thus in a generalized admittance controller, the expectation of the output
Directly dependent on Fx. Similarly, expectation of output
Directly dependent on Fy。
For thetaxAnd thetayThe control direction is based on the following: when the shaft hole is in a state relative to the pose
When theta is greater than thetax<0，
Wherein the content of the first and second substances,
when the shaft hole is in a state D relative to the pose-1，D0，D1When theta is greater than thetax>0，
Due to F in the assembly processzConstant positive, FxAnd MyCan uniquely judge thetaxPositive and negative. Thus in a generalized admittance controller, the expectation of the output
Directly dependent on FxAnd MyRelative magnitude relationship of (a). Similarly, expectation of output
Directly dependent on FyAnd MxRelative magnitude relationship of (a).
According to the above analysis process, the task information matrix a of the generalized admittance controller is designed as:
in the generalized admittance control rate, the method for realizing the direction control through a matrix has the advantages of improving the stability of system control by combining task model information. The most effective reduction of the additional assembly forces generated during the assembly process can be ensured.
In the generalized admittance control rate, the implementation method for adjusting the control quantity is as follows:
admittance control parameters M of different parameters according to characteristics of shaft hole assembly taskd，Dd，KdHas different characteristics. The motion characteristics of the shaft centerline insertion depth l are different from those of the other four parameters during the assembly task. Due to FrfrAccording to the nominal size of the shaft hole and the reference pose xrfrCalculated and the actual assembly force is changed under the influence of uncertainty of the assembly object, so thatIt cannot be directly used as a control basis. To eliminate the effect of the assembly object uncertainty on the accuracy of the control system, the admittance control parameter for the shaft centerline insertion depth l should be sufficiently large. In the assembly task, except the insertion depth l of the shaft center line, the admittance control parameters of the rest four-dimensional motion parameters should be small. For the admittance control parameters of the rest four-dimensional motion parameters, when the admittance control parameters are relatively small in a certain range, the system response rapidity is improved, and the stability is reduced; when the admittance control parameter is relatively large in a certain range, the system response rapidity is reduced, and the stability is improved. In order to balance the stability and the rapidity of the system, a variable impedance control mode is adopted.
An achievable variable impedance control method is that firstly, a group of relatively large admittance control parameters are determined as an upper bound according to the system rapidity and a group of relatively small admittance control parameters are determined as a lower bound according to the system stability by adjusting admittance control parameters. In the whole process from beginning to end of the assembly task, the admittance control parameters are set to be gradually increased from the lower bound to the upper bound by using a linear interpolation mode. The rapidity of the initial stage of assembly and the stability of the final stage of assembly are ensured.
In the generalized admittance control rate, the implementation method for adjusting the control quantity has the advantages that the accuracy in the insertion depth direction is improved by setting the admittance control parameter with a sufficient size for the insertion depth l of the central axis of the shaft. The variable admittance control parameters are set for the rest four-dimensional motion parameters except the insertion depth l of the axis center line, so that the rapidity and the stability of the system are balanced.
According to the robot interference shaft hole assembling method based on the force position state mapping model, a robot assembling system of the interference shaft hole is constructed; establishing a state mapping model of the relative pose of the shaft hole and the interaction force; acquiring a current interaction force through a force sensor signal in the robot assembly system; and obtaining the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of the system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller. Therefore, the assembly of the interference shaft hole is realized in a generalized admittance control mode by establishing a state mapping model of the relative pose and interaction force of the interference assembly of the shaft hole and using a robot power control technology.
In order to realize the embodiment, the application further provides a robot interference shaft hole assembling device based on the force position state mapping model.
Fig. 10 is a schematic structural diagram of a robot interference shaft hole assembling device based on a force position state mapping model according to an embodiment of the present application.
As shown in fig. 10, the robot interference shaft hole assembling device based on the force position state mapping model includes: a building module 210, a building module 220, an obtaining module 230, and a processing module 240.
And the building module 210 is used for building the robot assembly system of the interference shaft hole.
And the establishing module 220 is used for establishing a state mapping model of the shaft hole relative pose and the interaction force.
An obtaining module 230, configured to obtain the current interaction force through a signal of a force sensor in the robot assembly system.
And the processing module 240 is configured to obtain a current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determine a control direction of the system controller according to the current state, and perform interference shaft hole assembly according to the control direction and control parameters of the system controller.
In an embodiment of the present application, a robotic assembly system comprises: the robot comprises a force sensor, a force sensor signal amplifier, a force sensor data acquisition card, a robot controller, a system controller, a circular hole, a circular shaft, a shaft holder and a hole holder; the circular hole is in interference fit with the circular shaft; the building module 210 is specifically configured to: the robot base is fixed on the table top, the tail end of the robot is fixedly connected with the shaft holder, and the shaft holder holds a shaft to be assembled; the lower end of the force sensor is fixedly connected with the table board, the upper end of the force sensor is fixedly connected with the hole clamp holder, and the hole clamp holder clamps a hole to be assembled; the force sensor signal is uploaded to the system controller through the force sensor signal amplifier and the force sensor data acquisition card; control instructions of the system controller are sent to the robot via the robot controller.
In this embodiment of the application, the establishing module 220 is specifically configured to: in the state mapping model, the radius of the shaft is R, the inner radius of the hole matched with the shaft is R, the matching property is interference, and the outer radius of the hole is R1The depth of the hole is L, the origin of a hole coordinate system is defined at the center of the circle of the upper end surface of the hole, the X-axis direction is the same as the X-axis direction of the force sensor, the Y-axis direction is the same as the Y-axis direction of the force sensor, the Z-axis direction is the same as the Z-axis direction of the force sensor, and the Z-axis direction is also the axial direction of the hole; integrating the contact area of the shaft and the hole to obtain an interaction force corresponding to the relative pose of the specific shaft hole; acquiring detection data of a force sensor as force and moment applied to the center of the bottom end face of the hole, performing stress analysis by taking the hole as an object, integrating the stress of all contact positions by taking the center of the bottom end face of the hole as an equivalent point of analysis, and then equivalently obtaining force and moment acting on the center of the bottom end face of the hole, thereby acquiring an initial state mapping model of the relative pose of the shaft hole and the interaction force; and simplifying the initial state mapping model to obtain the state mapping model.
In the embodiment of the application, a double closed-loop control frame is adopted for pose control of the robot, the robot executes position closed loop, and the robot executes force closed loop under the control of a generalized admittance controller;
the generalized admittance control rate is:
wherein x isrfrFor the reference pose of the axis in the assembly process,
is xrfrThe first derivative of (a) is,
is xrfrSecond derivative of, Md，Dd，KdIs a control parameter of the generalized admittance controller, A is a directional control matrix of the generalized admittance controller, xdA desired parameter for the output of the generalized admittance controller,
is xdThe first derivative of (a) is,
is xdSecond derivative of (F)extFor the equivalent force vector of the stress at the bottom of the hole end face, F, caused by deformation of the shaft hole during assemblyrfrAccording to the nominal size of the axle hole and according to the reference pose xrfrThe obtained reference force is calculated.
In an embodiment of the present application, the apparatus further includes: and the adjusting module is used for adjusting the current interaction force acquired by the force sensor signal when the position of the hole is not horizontally placed or when the hole is in a motion state.
The robot interference shaft hole assembling device based on the force position state mapping model comprises a robot assembling system for constructing interference shaft holes; establishing a state mapping model of the relative pose of the shaft hole and the interaction force; acquiring a current interaction force through a force sensor signal in the robot assembly system; and obtaining the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of the system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller. Therefore, the assembly of the interference shaft hole is realized in a generalized admittance control mode by establishing a state mapping model of the relative pose and interaction force of the interference assembly of the shaft hole and using a robot power control technology.
It should be noted that the foregoing explanation of the embodiment of the method for assembling the interference shaft hole of the robot based on the force position state mapping model is also applicable to the apparatus for assembling the interference shaft hole of the robot based on the force position state mapping model in this embodiment, and details are not repeated here.
In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing steps of a custom logic function or process, and alternate implementations are included within the scope of the preferred embodiment of the present application in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present application.
The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.
It should be understood that portions of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. If implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes one or a combination of the steps of the method embodiments.
In addition, functional units in the embodiments of the present application may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. The integrated module, if implemented in the form of a software functional module and sold or used as a stand-alone product, may also be stored in a computer readable storage medium.
The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc. Although embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and that variations, modifications, substitutions and alterations may be made to the above embodiments by those of ordinary skill in the art within the scope of the present application.
Claims (8)
1. A robot interference shaft hole assembling method based on a force position state mapping model is characterized by comprising the following steps:
constructing a robot assembly system of the interference shaft hole;
establishing a state mapping model of the shaft hole relative pose and the interaction force, wherein the establishing of the state mapping model of the shaft hole relative pose and the interaction force comprises the following steps: in the state mapping model, the radius of the shaft is R, the inner radius of the hole matched with the shaft is R, the matching property is interference, and the outer radius of the hole is R1The depth of the hole is L, the origin of a hole coordinate system is defined at the center of the circle of the upper end surface of the hole, the X-axis direction is the same as the X-axis direction of the force sensor, the Y-axis direction is the same as the Y-axis direction of the force sensor, the Z-axis direction is the same as the Z-axis direction of the force sensor, and the Z-axis direction is also the axial direction of the hole; integrating the contact area of the shaft and the hole to obtain an interaction force corresponding to the relative pose of the specific shaft hole; obtainingThe detection data of the force sensor is used as force and moment applied to the center of the end face of the bottom of the hole, the hole is used as an object to carry out stress analysis, the center of the end face of the bottom of the hole is used as an equivalent point of the analysis, the stress of all contact positions is integrated and then is equivalent to the force and moment acting on the center of the end face of the bottom of the hole, and an initial state mapping model of the relative pose of the shaft hole and the interaction force is obtained; simplifying the initial state mapping model to obtain the state mapping model;
acquiring a current interaction force through a force sensor signal in the robot assembly system;
and acquiring the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of a system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller.
2. The method of claim 1, wherein the robotic assembly system comprises: the robot comprises a force sensor, a force sensor signal amplifier, a force sensor data acquisition card, a robot controller, a system controller, a circular hole, a circular shaft, a shaft holder and a hole holder; the fit property of the round hole and the round shaft is interference fit, and the robot assembly system for constructing the interference shaft hole comprises a circular hole and a circular shaft;
the robot base is fixed on the table top, the tail end of the robot is fixedly connected with the shaft holder, and the shaft holder holds a shaft to be assembled;
the lower end of the force sensor is fixedly connected with the table board, the upper end of the force sensor is fixedly connected with the hole clamp holder, and the hole clamp holder clamps a hole to be assembled;
the force sensor signal is uploaded to the system controller through the force sensor signal amplifier and the force sensor data acquisition card;
control instructions of the system controller are sent to the robot via the robot controller.
3. The method of claim 1, wherein pose control of a robot employs a dual closed loop control framework, the robot performing position closed loop, the robot performing force closed loop under control of a generalized admittance controller;
the generalized admittance control rate is:
wherein x isrfrFor the reference pose of the axis in the assembly process,
is xrfrThe first derivative of (a) is,
is xrfrSecond derivative of, Md，Dd，KdIs a control parameter of the generalized admittance controller, A is a directional control matrix of the generalized admittance controller, xdA desired parameter for the output of the generalized admittance controller,
is xdThe first derivative of (a) is,
is xdSecond derivative of (F)extFor the equivalent force vector of the stress at the bottom of the hole end face, F, caused by deformation of the shaft hole during assemblyrfrAccording to the nominal size of the axle hole and according to the reference pose xrfrThe obtained reference force is calculated.
4. The method of claim 1, further comprising:
and when the position of the hole is not horizontally placed or the hole is in a motion state, the current interaction force acquired by the force sensor signal is adjusted.
5. The utility model provides a robot interference shaft hole assembly quality based on force position state mapping model which characterized in that includes:
the construction module is used for constructing a robot assembly system of the interference shaft hole;
the establishing module is used for establishing a state mapping model of the relative pose of the shaft hole and the interaction force, wherein the establishing module is specifically used for: in the state mapping model, the radius of the shaft is R, the inner radius of the hole matched with the shaft is R, the matching property is interference, and the outer radius of the hole is R1The depth of the hole is L, the origin of a hole coordinate system is defined at the center of the circle of the upper end surface of the hole, the X-axis direction is the same as the X-axis direction of the force sensor, the Y-axis direction is the same as the Y-axis direction of the force sensor, the Z-axis direction is the same as the Z-axis direction of the force sensor, and the Z-axis direction is also the axial direction of the hole; integrating the contact area of the shaft and the hole to obtain an interaction force corresponding to the relative pose of the specific shaft hole; acquiring detection data of a force sensor as force and moment applied to the center of the bottom end face of the hole, performing stress analysis by taking the hole as an object, integrating the stress of all contact positions by taking the center of the bottom end face of the hole as an equivalent point of analysis, and then equivalently obtaining force and moment acting on the center of the bottom end face of the hole, thereby acquiring an initial state mapping model of the relative pose of the shaft hole and the interaction force; simplifying the initial state mapping model to obtain the state mapping model;
the acquisition module is used for acquiring the current interaction force through a force sensor signal in the robot assembly system;
and the processing module is used for acquiring the current state of the relative pose of the shaft hole according to the state mapping model and the current interaction force, determining the control direction of the system controller according to the current state, and assembling the interference shaft hole according to the control direction and the control parameters of the system controller.
6. The apparatus of claim 5, wherein the robotic assembly system comprises: the robot comprises a force sensor, a force sensor signal amplifier, a force sensor data acquisition card, a robot controller, a system controller, a circular hole, a circular shaft, a shaft holder and a hole holder; the circular hole is in interference fit with the circular shaft; the building module is specifically configured to:
the robot base is fixed on the table top, the tail end of the robot is fixedly connected with the shaft holder, and the shaft holder holds a shaft to be assembled;
the lower end of the force sensor is fixedly connected with the table board, the upper end of the force sensor is fixedly connected with the hole clamp holder, and the hole clamp holder clamps a hole to be assembled;
the force sensor signal is uploaded to the system controller through the force sensor signal amplifier and the force sensor data acquisition card;
control instructions of the system controller are sent to the robot via the robot controller.
7. The apparatus of claim 5, wherein pose control of a robot employs a dual closed loop control framework, the robot performing position closed loop, the robot performing force closed loop under control of a generalized admittance controller;
the generalized admittance control rate is:
wherein x isrfrFor the reference pose of the axis in the assembly process,
is xrfrThe first derivative of (a) is,
is xrfrSecond derivative of, Md，Dd，KdIs a control parameter of the generalized admittance controller, A is a directional control matrix of the generalized admittance controller, xdA desired parameter for the output of the generalized admittance controller,
is xdThe first derivative of (a) is,
is xdSecond derivative of (F)extFor the equivalent force vector of the stress at the bottom of the hole end face, F, caused by deformation of the shaft hole during assemblyrfrAccording to the nominal size of the axle hole and according to the reference pose xrfrThe obtained reference force is calculated.
8. The apparatus of claim 5, further comprising:
and the adjusting module is used for adjusting the current interaction force acquired by the force sensor signal when the position of the hole is not horizontally placed or when the hole is in a motion state.
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