CN107139174B - Control device and method for plane parallel mechanism driven by double five-rod mechanism - Google Patents
Control device and method for plane parallel mechanism driven by double five-rod mechanism Download PDFInfo
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- CN107139174B CN107139174B CN201710507051.7A CN201710507051A CN107139174B CN 107139174 B CN107139174 B CN 107139174B CN 201710507051 A CN201710507051 A CN 201710507051A CN 107139174 B CN107139174 B CN 107139174B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
- B25J9/1615—Programme controls characterised by special kind of manipulator, e.g. planar, scara, gantry, cantilever, space, closed chain, passive/active joints and tendon driven manipulators
- B25J9/1623—Parallel manipulator, Stewart platform, links are attached to a common base and to a common platform, plate which is moved parallel to the base
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/003—Programme-controlled manipulators having parallel kinematics
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
- B25J9/1628—Programme controls characterised by the control loop
- B25J9/1643—Programme controls characterised by the control loop redundant control
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Abstract
The invention discloses a control device and a control method for a plane parallel mechanism driven by a double five-rod mechanism, wherein the device comprises a plane parallel mechanism body and a control unit, wherein the plane parallel mechanism body comprises a movable platform, a passive motion branched chain and two plane five-rod mechanisms; a three-axis acceleration sensor is arranged on the movable platform; each plane five-rod mechanism comprises two direct drive rotating motors, two driving rods and two driven rods; the passive motion branched chain comprises a bearing assembly and two passive rods; the control unit is respectively connected with the three-axis acceleration sensor and the direct drive rotating motor. The two plane five-bar mechanisms are used as the active motion branched chains, the two plane five-bar mechanisms are directly driven by the rotating motor, and the acceleration sensor is used for closed-loop feedback, so that the parallel mechanism has the advantages of high control precision, quick response of closed-loop control, elimination of singularity of the parallel mechanism and the like.
Description
Technical Field
The invention relates to a plane parallel mechanism control device, in particular to a plane parallel mechanism control device and method driven by a double five-rod mechanism, and belongs to the field of plane parallel mechanism design and control.
Background
The parallel robot is characterized in that a plurality of freedom end effectors are connected with a fixed foundation through two or more independent moving branched chains, the parallel robot has the application advantages of high speed, high precision and high bearing capacity compared with a series robot, a movable platform at the tail end of the parallel robot can realize high-speed movement, precise positioning and large-mass load bearing, but the parallel mechanism has the defects of small working space, singular configuration, vibration and the like in the movement process due to the structural characteristics, and the performance of the parallel mechanism is greatly influenced.
The redundancy driving method is an effective method for reducing or eliminating singularities, which is proposed at present, and the method has two implementation modes: 1) Changing a part of passive joints into active joints on the basis of a normal mechanism, 2) adding a new branched chain on the premise of ensuring the freedom degree of the mechanism to be unchanged, and introducing redundant drive to the branched chain. The former approach, although simple, can affect the mechanics dynamics by adding a driver to the passive joint, which increases the inertia of the system; the latter approach will certainly increase the complexity of the mechanism by introducing a new branched chain, but it will be more advantageous than the redundant driving method by introducing a new branched chain because it can easily mount the driver on the fixed base, can ensure the symmetry of the mechanism, and can also solve the problem of complex and multi-solution kinematics positive solution. How to introduce new branched chains and what kind of branched chains are the key to eliminate the strange problems and the like.
Disclosure of Invention
The invention aims to solve the defects of the prior art and provides a planar parallel mechanism control device driven by a double five-rod mechanism, which takes two planar five-rod mechanisms as active motion branched chains, is driven by directly driving a rotating motor and utilizes an acceleration sensor to carry out closed-loop feedback, so that the planar parallel mechanism control device has the advantages of high control precision, quick response of closed-loop control, elimination of singularity of a parallel mechanism and the like.
The invention also aims to provide a plane parallel mechanism control method based on the device.
The purpose of the invention can be achieved by adopting the following technical scheme:
the plane parallel mechanism control device driven by the double five-rod mechanism comprises a plane parallel mechanism body and a control unit, wherein the plane parallel mechanism body comprises a movable platform, a driven motion branched chain and two plane five-rod mechanisms;
the movable platform is a triangular flat plate and is provided with two three-axis acceleration sensors;
each plane five-rod mechanism comprises two direct-drive rotating motors, two driving rods and two driven rods, wherein incremental encoders are arranged inside the two direct-drive rotating motors, one ends of the two driving rods are respectively connected with the two direct-drive rotating motors, the other ends of the two driving rods are respectively in rotary connection with one ends of the two driven rods, and the other ends of the two driven rods are in rotary connection with one corner of the movable platform;
the passive moving branched chain comprises a bearing assembly and two passive rods, one end of one passive rod is fixedly connected with the bearing assembly, the other end of the passive rod is rotatably connected with one end of the other passive rod, and the other end of the other passive rod is rotatably connected with one corner of the moving platform;
and the control unit is respectively connected with the three-axis acceleration sensor and the direct drive rotating motor.
Furthermore, the two triaxial acceleration sensors are respectively a first triaxial acceleration sensor and a second triaxial acceleration sensor, the first triaxial acceleration sensor is installed at the center of the movable platform, the second triaxial acceleration sensor is installed at the position 30 mm-50 mm away from the center of the movable platform, and the first triaxial acceleration sensor and the second triaxial acceleration sensor are located in a horizontal state.
Further, in each planar five-bar mechanism, the two driving bars are respectively a first driving bar and a second driving bar, and the two driven bars are respectively a first driven bar and a second driven bar;
the first driving rod and the second driving rod are located on the same plane, the first driven rod is located above the first driving rod, the second driven rod is located below the second driving rod, and the movable platform is located between the first driven rod and the second driven rod.
Furthermore, in the passive motion branched chain, the two passive rods are respectively a passive primary rod and a passive secondary rod;
the driven primary rod, the first driving rod and the second driving rod are located on the same plane, the driven secondary rod and the first driven rod are located on the same plane, one end of the driven primary rod is fixedly connected with the bearing assembly, the other end of the driven primary rod is rotatably connected with one end of the driven secondary rod, and the other end of the driven secondary rod is rotatably connected with one corner of the movable platform.
Further, in the passive motion branch chain, the bearing assembly comprises a bearing sleeve and a bearing seat;
the bearing sleeve is inserted into the bearing seat, one end of the driven primary rod is fixedly connected with the bearing sleeve, the other end of the driven primary rod is hinged with one end of the driven secondary rod through the rotating shaft, and the other end of the driven secondary rod is hinged with one corner of the movable platform through the rotating shaft.
Furthermore, each plane five-rod mechanism further comprises two flange plate connecting pieces, two direct-drive rotating motors are respectively connected with the two flange plate connecting pieces, one ends of the two driving rods are respectively fixed on the two flange plate connecting pieces through screws, the other ends of the two driving rods are respectively hinged with one ends of the two driven rods through rotating shafts, and the other ends of the two driven rods are rotatably hinged with one corner of the movable platform through the rotating shafts.
Furthermore, the control unit comprises a computer, a data acquisition card, a motion control card, an A/D conversion circuit and a direct drive rotating motor servo unit, wherein the computer is respectively connected with the data acquisition card and the motion control card, the data acquisition card is connected with the three-axis acceleration sensor through the A/D conversion circuit, and the motion control card is connected with the direct drive rotating motor through the direct drive rotating motor servo unit;
the two triaxial acceleration sensors detect the translational acceleration information and the rotational acceleration information of the movable platform, the translational acceleration information and the rotational acceleration information are subjected to A/D conversion through an A/D conversion circuit, stored in a data acquisition card and called and processed by a computer;
the incremental encoder inside the direct drive rotating motor detects the position information of the motor shaft, and the position information is processed by the servo unit and the motion control card of the direct drive rotating motor and fed back to the computer for calculating the controlled variable.
Furthermore, the plane parallel mechanism body also comprises a static platform, the static platform is a square section bar seat, the bottom of the static platform is provided with four supporting legs, and a transverse bracket is arranged between every two adjacent supporting legs;
the two direct-drive rotating motors of one plane five-bar mechanism and the two direct-drive rotating motors of the other plane five-bar mechanism are symmetrical about the central line of the top plane of the static platform, each plane five-bar mechanism further comprises two motor bases, and each direct-drive rotating motor is fixed on the static platform through one motor base;
and the bearing assembly of the passive moving branched chain is fixed on the static platform.
The other purpose of the invention can be achieved by adopting the following technical scheme:
the plane parallel mechanism control method based on the device comprises the following steps:
firstly, according to a given track, a target position and a moving platform pose, inverse kinematics solution is carried out in a computer to obtain the output quantity of each motor shaft, the computer outputs the control quantity to a direct drive rotating motor servo unit through a motion control card to control the direct drive rotating motor to rotate, and therefore the moving platform moves;
secondly, in the motion process of the movable platform, two triaxial acceleration sensors on the movable platform measure the translation acceleration information and the rotation acceleration information of the movable platform in real time, the motion information is subjected to A/D conversion through an A/D conversion circuit, stored in a data acquisition card and called and processed by a computer;
meanwhile, an incremental encoder inside the direct drive rotating motor detects the position information of the motor shaft, performs related processing through a servo unit and a motion control card of the direct drive rotating motor, and feeds back the position information to the computer;
step three, the computer calculates a control signal through a control algorithm according to the motion information of the movable platform and the position information of the motor shaft obtained in the step two, the control signal firstly passes through a motion control card and then is output to a servo unit of the direct drive rotating motor to drive the direct drive rotating motor to rotate, and then the movable platform is controlled to move to a specified position according to an expected track;
and step four, repeating the test, and modifying the control parameters to enable the control precision to meet the expected requirement.
Further, in the second step, the two three-axis acceleration sensors on the moving platform measure the translational acceleration information and the rotational acceleration information of the moving platform in real time, which are specifically as follows:
the two triaxial acceleration sensors are respectively a first triaxial acceleration sensor and a second triaxial acceleration sensor, the first triaxial acceleration sensor is installed at the center of the movable platform, and the second triaxial acceleration sensor is installed at a position 30-50 mm away from the center of the movable platform;
the first triaxial acceleration sensor measures the acceleration a in the x direction x1 And acceleration a in the y direction y1 The acceleration a in the x direction is measured by the second triaxial acceleration sensor x2 And acceleration a in the y direction y2 Acceleration in the x direction at the center of the movable platform
Acceleration in y direction at center of moving platform
The rotational acceleration at the center of the movable platform is
And d is the distance between the second triaxial acceleration sensor and the center of the movable platform.
Compared with the prior art, the invention has the following beneficial effects:
1. on the basis of a plane 3-RRR (rotation-rotation branch) parallel mechanism, a new branched chain is respectively introduced into two parallel branched chains to form a plane five-rod mechanism serving as an active motion branched chain, and a third parallel branched chain serves as a passive motion branched chain; the driving rod of the plane five-rod mechanism is driven by a direct-drive rotating motor, a speed reducer is not included, the influence of a transmission mechanism can be eliminated, and the direct-drive rotating motor has small friction and stable movement in the driving process, so the driving and control effects are better; the moving platform is provided with two three-axis acceleration sensors, the two three-axis acceleration sensors are adopted to measure the motion information of the moving platform at the tail end, a full closed loop feedback circuit is formed, and the motion of the moving platform can be accurately controlled according to the feedback information, so that the moving platform can stably, accurately and quickly reach an appointed position.
2. The plane five-bar mechanism of the invention simplifies the kinematics forward and reverse solution of the whole plane parallel mechanism, improves the operation performance of the whole plane parallel mechanism, but does not lose the degree of freedom of the tail end moving platform.
3. The two plane five-bar mechanisms of the invention both adopt two direct drive rotating motors, are combined with a control unit, namely four sets of motor systems, and the tail end platform has only three degrees of freedom, so that drive redundancy is formed, and the control is more flexible.
4. The length of the driving rod and the length of the driven rod of the plane five-rod mechanism can be reasonably designed according to actual needs, and the condition that the two rods are parallel to each other is avoided, so that the singular configuration of the plane parallel mechanism is avoided.
Drawings
Fig. 1 is a schematic view of the overall structure of a planar parallel mechanism control device according to embodiment 1 of the present invention.
Fig. 2 is a plan view of a planar parallel mechanism body in the planar parallel mechanism control device according to embodiment 1 of the present invention.
Fig. 3 is a left side view of the planar parallel mechanism body in the planar parallel mechanism control device according to embodiment 1 of the present invention.
Fig. 4 is a schematic structural diagram of a movable platform mounted three-axis acceleration sensor in the planar parallel mechanism control device according to embodiment 1 of the present invention.
Fig. 5 is a schematic structural view of a planar five-bar mechanism in the planar parallel mechanism control device according to embodiment 1 of the present invention.
Fig. 6 is a schematic structural diagram of a passive moving branch chain in the planar parallel mechanism control device according to embodiment 1 of the present invention.
Fig. 7 is an acceleration calculation diagram of the movable platform in the planar parallel mechanism control device according to embodiment 1 of the present invention.
The system comprises a movable platform 1, a static platform 2, a first three-axis acceleration sensor 3, a second three-axis acceleration sensor 4, a supporting leg 5, a transverse support 6, a first direct drive rotating motor 7, a second direct drive rotating motor 8, a first motor base 9, a second motor base 10, a first driving rod 11, a second driving rod 12, a first flange plate connecting piece 13, a second flange plate connecting piece 14, a first driven rod 15, a second driven rod 16, a passive primary rod 17, a passive secondary rod 18, a bearing sleeve 19, a bearing seat 20, a computer 21, a data acquisition card 22, a motion control card 23, an A/D conversion circuit 24 and a direct drive rotating motor servo unit 25.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Example 1:
as shown in fig. 1 to fig. 3, the present embodiment provides a planar parallel mechanism control device driven by a double five-bar mechanism, the device includes a planar parallel mechanism body and a control unit, the planar parallel mechanism body includes a movable platform 1, a static platform 2, a passive moving branched chain and two planar five-bar mechanisms, the connection of the dotted line in fig. 1 represents the connection diagram of an electrical signal and the planar parallel mechanism body, and the directional arrow represents the transmission direction of the detection and control signal flow;
as shown in fig. 1 to 4, the movable platform 1 is a triangular flat plate, in this embodiment, an equilateral triangular flat plate is preferably used, three corners are provided with three holes, the three corners are respectively connected with the passive motion branch chain and the two plane five-bar mechanisms through rotating shafts, a first three-axis acceleration sensor 3 and a second three-axis acceleration sensor 4 are mounted on the movable platform 1, the first three-axis acceleration sensor 3 is mounted at the center of the movable platform 1, the second three-axis acceleration sensor 4 is mounted at a position 40mm away from the center of the movable platform 1, the first three-axis acceleration sensor 3 and the second three-axis acceleration sensor 4 are located in a horizontal state, and the first three-axis acceleration sensor 3 and the second three-axis acceleration sensor 4 are used for detecting translational acceleration information and rotational acceleration information of the movable platform 1;
in this embodiment, the first triaxial acceleration sensor 3 and the second triaxial acceleration sensor 4 both adopt capacitance sensors of Kistler corporation, the model number of which is 8395a010AT, the sensitivity of which is 400mV/g, and the measuring range of which is ± 10g, and because an amplifying circuit is arranged in the capacitance sensors, the capacitance sensors need to be powered by an external power supply.
The static platform 2 is a square section bar seat and is used for supporting the whole plane parallel mechanism body, the bottom of the static platform is provided with four supporting legs 5, and a transverse bracket 6 is arranged between every two adjacent supporting legs 5;
as shown in fig. 1 to 3 and 5, each planar five-bar mechanism includes a first direct-drive rotating electrical machine 7, a second direct-drive rotating electrical machine 8, a first electrical machine base 9, a second electrical machine base 10, a first driving bar 11, a second driving bar 12, a first flange connecting piece 13, a second flange connecting piece 14, a first driven bar 15 and a second driven bar 16, the first direct-drive rotating electrical machine 7 is fixed on the stationary platform 2 through the first electrical machine base 9 and is connected with the first flange connecting piece 13, one end of the first driving bar 11 is fixed on the first flange connecting piece 13 through a screw, and the other end is hinged with one end of the first driven bar 15 through a rotating shaft; similarly, the second direct-drive rotating motor 8 is fixed on the stationary platform 2 through a second motor base 10 and is connected with a second flange connecting piece 14, one end of the second driving rod 12 is fixed on the second flange connecting piece 14 through a screw, and the other end of the second driving rod is hinged with one end of the second driven rod 16 through a rotating shaft; the other ends of the first driving rod 11 and the second driven rod 16 are hinged with one corner of the movable platform 1 through a rotating shaft to form a composite hinge structure; the first direct drive rotating motor 7 drives to sequentially drive the first driving rod 11 and the first driven rod 15 to move, meanwhile, the second direct drive rotating motor 5 drives to sequentially drive the second driving rod 9 and the second driven rod 16 to move, so that the movable platform 1 moves, and the passive motion branched chain is forced to move under the motion of the movable platform 1, so that the effects of constraint and bearing are achieved.
In the present embodiment, the first driving link 11 and the second driving link 12 are located on the same plane, the first driven link 15 is located above the first driving link 11, the second driven link 16 is located below the second driving link 12, and the movable platform 1 is located between the first driven link 15 and the second driven link 16; the first direct drive rotating motor 7 and the second direct drive rotating motor 8 are motors produced by the Athens on Singapore, the model is ADR135-A90, the rated torque is 5.2Nm, and the rated rotating speed is 147rpm, and the direct drive rotating motors are widely applied to various industries due to the unique characteristics of low speed, large torque, high precision positioning, high response speed, simple structure, reduced mechanical loss, low noise, less maintenance and the like except the characteristics of a servo motor; the two direct-drive rotating motors of one plane five-bar mechanism and the two direct-drive rotating motors of the other plane five-bar mechanism are symmetrical about the central line of the top plane of the static platform 2.
As shown in fig. 1 to 3 and 6, the passive moving branched chain includes a bearing assembly, a passive primary rod 17 and a passive secondary rod 18, the bearing assembly includes a bearing sleeve 19 and a bearing seat 20, a rotating shaft end of the bearing sleeve 19 is inserted into the bearing seat 20, one end of the passive primary rod 17 is fixedly connected with the bearing sleeve 19, the other end of the passive primary rod is hinged with one end of the passive secondary rod 18 through a rotating shaft, and the other end of the passive secondary rod 18 is hinged with one corner of the movable platform 1 through a rotating shaft.
In this embodiment, the passive primary lever 17, the first driving lever 11 and the second driving lever 12 are located on the same plane, the passive secondary lever 18 and the first driven lever 15 are located on the same plane, and when the movable platform 1 moves, the passive secondary lever 18 and the passive primary lever 17 are sequentially driven to move.
The control unit comprises a computer 21, a data acquisition card 22, a motion control card 23, an A/D conversion circuit 24 and a direct drive rotating motor servo unit 25, the computer 21 is respectively connected with the data acquisition card 22 and the motion control card 23, the data acquisition card 22 is connected with a first three-axis acceleration sensor 3 and a second three-axis acceleration sensor 4 through the A/D conversion circuit 24, and the motion control card 23 is connected with a first direct drive rotating motor 7 and a second direct drive rotating motor 8 of each plane five-bar mechanism through the direct drive rotating motor servo unit 25.
The first triaxial acceleration sensor 3 and the second triaxial acceleration sensor 4 detect the translation acceleration information and the rotation acceleration information of the movable platform 1, perform A/D conversion through an A/D conversion circuit 24, store the information in a data acquisition card, and call and process the information by a computer; incremental encoders inside the first direct drive rotating motor 7 and the second direct drive rotating motor 8 of each plane five-bar mechanism detect position information of a motor shaft, perform related processing through a direct drive rotating motor servo unit 25 and a motion control card 23, feed back the processed information to the computer 21, and calculate a control quantity through the computer 21.
In the present embodiment, the data acquisition card 22 is a PCI-8193 manufactured by Beijing Altai technologies, inc.; the computer 21 is a computer with the CPU model of intel-Core i74790, the frequency of 3.6Hz and the memory of 4G; the motion control card 23 is PMAC2 of the PMAC card series, DELTA TAU, usa, and first configures the drive mode, electronic gear ratio, and PMAC2 card I variables, the motion mode used is the position control mode, the drive load is set to medium, corresponding to a value of 1, stiffness is neutral, and value is 3, and the electronic gear ratio is set to 0.04 ° per pulse for motor rotation.
Compared with a planar 3-RRR parallel mechanism, the planar parallel mechanism control device of the embodiment introduces new branched chains into two parallel branched chains respectively to form a planar five-rod mechanism, the third parallel branched chain is changed from active to passive (passive moving branched chain), the degree of freedom of the mechanism is not changed, and three degrees of freedom are still provided, namely two degrees of freedom in the horizontal direction and one degree of freedom in the rotating direction, and four driving motors are provided (two for each planar five-rod mechanism), so that driving redundancy is formed, the redundancy of the mechanism is increased, and the control is more flexible; by adopting the plane five-bar mechanism, due to the characteristics of the plane five-bar mechanism, the kinematics forward solution and the kinematics backward solution of the whole device are easy, so the operability of the whole device is higher; in addition, due to the structural characteristics of the plane five-bar mechanisms, the driving force of the plane five-bar mechanisms on the moving platform cannot be parallel to the connecting line of the two composite hinge points at the same time, so that the singularity problem of a parallel mechanism can be solved; meanwhile, the driving rod of the plane five-rod mechanism utilizes a direct drive rotating motor as a driver, and does not need to pass through a speed reducer and other intermediate transmission mechanisms, so that the problems of friction force, clearance, nonlinearity and the like are solved, and the motion control precision and response speed of the mechanism are greatly improved.
As shown in fig. 1 to fig. 6, this embodiment further provides a method for controlling a planar parallel mechanism, where the method is implemented based on the foregoing apparatus, and includes the following steps:
firstly, according to a given track, a target position and a moving platform pose, inverse kinematics solution is carried out in a computer 29 to obtain the output quantity of each motor shaft, the computer 21 outputs the control quantity to a direct drive rotating motor servo unit 25 through a motion control card 23 to control the direct drive rotating motor to rotate, and therefore the moving platform 1 moves;
secondly, in the moving process of the moving platform 1, the first three-axis acceleration sensor 3 and the second three-axis acceleration sensor 4 on the moving platform 1 measure the translation acceleration information and the rotation acceleration information of the moving platform 1 in real time, the motion information is subjected to A/D conversion through an A/D conversion circuit 24, stored in a data acquisition card 22 and called and processed by a computer 21;
meanwhile, an incremental encoder inside the direct drive rotating motor detects the position information of the motor shaft, and the position information is subjected to related processing through a servo unit 25 of the direct drive rotating motor and a motion control card 23 and is fed back to the computer 21;
step three, the computer calculates a control signal through a control algorithm according to the motion information of the movable platform 1 and the position information of the motor shaft obtained in the step two, the control signal firstly passes through the motion control card 20 and then is output to the direct drive rotating motor servo unit 25 to drive the direct drive rotating motor to rotate, and then the control platform 1 is controlled to move to a specified position according to an expected track;
and step four, repeating the test, and modifying the control parameters to enable the control precision to meet the expected requirement.
As shown in fig. 7, in the second step, the two three-axis acceleration sensors on the movable platform measure the translational acceleration information and the rotational acceleration information of the movable platform in real time, which is specifically as follows:
three corner positions C of movable platform 1 1 、C 2 And C 3 The first triaxial acceleration sensor 3 measures the acceleration a in the x direction x1 And acceleration a in the y direction y1 The acceleration a in the x direction is measured by the second triaxial acceleration sensor 4 x2 And acceleration a in the y direction y2 Acceleration in the x direction at the center of the movable platform 1
Acceleration in the y direction at the center of the movable platform 1
The rotational acceleration at the center of the movable platform 1 is
Where d is the distance between the second triaxial acceleration sensor 4 and the center of the moving platform, i.e. 40mm.
Example 2:
the main characteristics of this embodiment are: the second triaxial acceleration sensor 4 is installed at a distance of 30mm or 50mm from the center of the movable platform 1. The rest is the same as example 1.
In summary, on the basis of a plane 3-RRR (rotation-rotation branch) parallel mechanism, a plane five-rod mechanism is formed by respectively introducing new branched chains into two parallel branched chains to serve as an active motion branched chain, and a third parallel branched chain serves as a passive motion branched chain; the driving rod of the plane five-rod mechanism is driven by a direct-drive rotating motor, a speed reducer is not included, the influence of a transmission mechanism can be eliminated, and the direct-drive rotating motor has small friction and stable movement in the driving process, so the driving and control effects are better; the moving platform is provided with two three-axis acceleration sensors, the two three-axis acceleration sensors are adopted to measure the motion information of the moving platform at the tail end, a full closed loop feedback circuit is formed, and the motion of the moving platform can be accurately controlled according to the feedback information, so that the moving platform can stably, accurately and quickly reach an appointed position.
The above description is only for the preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the scope of the present invention.
Claims (9)
1. Two five-bar mechanism driven plane parallel mechanism controlling means, its characterized in that: the device comprises a plane parallel mechanism body and a control unit, wherein the plane parallel mechanism body comprises a movable platform, a passive motion branched chain and two plane five-rod mechanisms;
the movable platform is a triangular flat plate and is provided with two three-axis acceleration sensors;
each plane five-rod mechanism comprises two direct-drive rotating motors, two driving rods and two driven rods, incremental encoders are arranged in the two direct-drive rotating motors, one ends of the two driving rods are respectively connected with the two direct-drive rotating motors, the other ends of the two driving rods are respectively in rotary connection with one ends of the two driven rods, and the other ends of the two driven rods are in rotary connection with one corner of the movable platform;
the passive motion branched chain comprises a bearing assembly and two passive rods, one end of one passive rod is fixedly connected with the bearing assembly, the other end of the passive rod is rotatably connected with one end of the other passive rod, and the other end of the other passive rod is rotatably connected with one corner of the movable platform;
the control unit is respectively connected with the three-axis acceleration sensor and the direct drive rotating motor;
the control unit comprises a computer, a data acquisition card, a motion control card, an A/D conversion circuit and a direct drive rotating motor servo unit, wherein the computer is respectively connected with the data acquisition card and the motion control card, the data acquisition card is connected with the three-axis acceleration sensor through the A/D conversion circuit, and the motion control card is connected with the direct drive rotating motor through the direct drive rotating motor servo unit;
the two triaxial acceleration sensors detect the translation acceleration information and the rotation acceleration information of the movable platform, the translation acceleration information and the rotation acceleration information are subjected to A/D conversion through an A/D conversion circuit, stored in a data acquisition card and called and processed by a computer;
the position information of the motor shaft is detected by an incremental encoder in the direct drive rotating motor, is subjected to relevant processing by a servo unit and a motion control card of the direct drive rotating motor and is fed back to a computer, and the computer is used for calculating the control quantity.
2. The control device of a planar parallel mechanism driven by a double five-rod mechanism according to claim 1, characterized in that: the two triaxial acceleration sensors are respectively a first triaxial acceleration sensor and a second triaxial acceleration sensor, the first triaxial acceleration sensor is installed at the center of the movable platform, the second triaxial acceleration sensor is installed at the position 30 mm-50 mm away from the center of the movable platform, and the first triaxial acceleration sensor and the second triaxial acceleration sensor are located in a horizontal state.
3. The control device of a planar parallel mechanism driven by a double five-rod mechanism according to claim 1, characterized in that: in each plane five-rod mechanism, the two driving rods are respectively a first driving rod and a second driving rod, and the two driven rods are respectively a first driven rod and a second driven rod;
the first driving rod and the second driving rod are located on the same plane, the first driven rod is located above the first driving rod, the second driven rod is located below the second driving rod, and the movable platform is located between the first driven rod and the second driven rod.
4. The control device of a planar parallel mechanism driven by a double five-rod mechanism according to claim 3, characterized in that: in the passive motion branched chain, the two passive rods are respectively a passive primary rod and a passive secondary rod;
the passive primary rod, the first driving rod and the second driving rod are located on the same plane, the passive secondary rod and the first driven rod are located on the same plane, one end of the passive primary rod is fixedly connected with the bearing assembly, the other end of the passive primary rod is rotatably connected with one end of the passive secondary rod, and the other end of the passive secondary rod is rotatably connected with one corner of the movable platform.
5. The dual five-bar mechanism driven planar parallel mechanism control device according to claim 4, wherein: in the passive motion branched chain, the bearing assembly comprises a bearing sleeve and a bearing seat;
the bearing sleeve is inserted into the bearing seat, one end of the driven primary rod is fixedly connected with the bearing sleeve, the other end of the driven primary rod is hinged with one end of the driven secondary rod through the rotating shaft, and the other end of the driven secondary rod is hinged with one corner of the movable platform through the rotating shaft.
6. The control device of a planar parallel mechanism driven by a double five-rod mechanism according to claim 1, characterized in that: each plane five-rod mechanism further comprises two flange plate connecting pieces, two direct-drive rotating motors are respectively connected with the two flange plate connecting pieces, one ends of the two driving rods are respectively fixed on the two flange plate connecting pieces through screws, the other ends of the two driving rods are respectively hinged with one ends of the two driven rods through rotating shafts, and the other ends of the two driven rods are rotatably hinged with one corner of the movable platform through the rotating shafts.
7. The control device of a planar parallel mechanism driven by a double five-rod mechanism according to claim 1, characterized in that: the plane parallel mechanism body further comprises a static platform, the static platform is a square section bar seat, the bottom of the static platform is provided with four supporting legs, and a transverse support is arranged between every two adjacent supporting legs;
the two direct-drive rotating motors of one plane five-bar mechanism and the two direct-drive rotating motors of the other plane five-bar mechanism are symmetrical about the central line of the top plane of the static platform, each plane five-bar mechanism further comprises two motor bases, and each direct-drive rotating motor is fixed on the static platform through one motor base;
and the bearing assembly of the passive moving branched chain is fixed on the static platform.
8. The planar parallel mechanism control method based on the device of claim 1, characterized in that: the method comprises the following steps:
firstly, performing inverse kinematics solution in a computer according to a given track, a given target position and a given moving platform pose to obtain the output quantity of each motor shaft, outputting the control quantity to a direct drive rotating motor servo unit by the computer through a motion control card, and controlling the direct drive rotating motor to rotate so as to move the moving platform;
secondly, in the motion process of the movable platform, two triaxial acceleration sensors on the movable platform measure the translation acceleration information and the rotation acceleration information of the movable platform in real time, the motion information is subjected to A/D conversion through an A/D conversion circuit, stored in a data acquisition card and called and processed by a computer;
meanwhile, an incremental encoder inside the direct drive rotating motor detects the position information of the motor shaft, performs related processing through a servo unit and a motion control card of the direct drive rotating motor, and feeds back the position information to the computer;
step three, the computer calculates a control signal through a control algorithm according to the motion information of the movable platform and the position information of the motor shaft obtained in the step two, the control signal firstly passes through a motion control card and then is output to a servo unit of the direct drive rotating motor to drive the direct drive rotating motor to rotate, and then the movable platform is controlled to move to a specified position according to an expected track;
and step four, repeating the test, and modifying the control parameters to enable the control precision to meet the expected requirement.
9. The planar parallel mechanism control method according to claim 8, characterized in that: in the second step, two triaxial acceleration sensors on the moving platform measure the translation acceleration information and the rotation acceleration information of the moving platform in real time, and the method specifically comprises the following steps:
the two triaxial acceleration sensors are respectively a first triaxial acceleration sensor and a second triaxial acceleration sensor, the first triaxial acceleration sensor is installed at the center of the movable platform, and the second triaxial acceleration sensor is installed at a position 30-50 mm away from the center of the movable platform;
the first triaxial acceleration sensor measures the acceleration a in the x direction x1 And acceleration a in the y direction y1 The acceleration a in the x direction is measured by the second three-axis acceleration sensor x2 And acceleration a in the y direction y2 Acceleration in the x direction at the center of the moving platform
Acceleration in y direction at center of moving platform
The rotational acceleration at the center of the movable platform is
And d is the distance between the second triaxial acceleration sensor and the center of the movable platform.
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