KR101730909B1

KR101730909B1 - Wearing robot and variable impedance controlling method thereof

Info

Publication number: KR101730909B1
Application number: KR1020150123806A
Authority: KR
Inventors: 김홍철; 이상훈; 신영준
Original assignee: 국방과학연구소
Priority date: 2015-09-01
Filing date: 2015-09-01
Publication date: 2017-05-04
Also published as: KR20170027187A

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a wearable robot capable of variably controlling an impedance parameter (stiffness, damping, etc.) based on a motion state and a variable impedance control method thereof. Calculating and storing the joint impedance value according to the human body movement according to the first embodiment; Determining a walking state of the wearer with a sensor attached to the soles of the wearer robot; Determining a motion state through robot posture estimation using an upper body backpack part of the wearer robot and a tilt measurement sensor attached to the sole; And driving the joint driving part by variably applying the stored joint impedance value according to the determined gait state and motion state.

Description

WEARING ROBOT AND VARIABLE IMPEDANCE CONTROLLING METHOD THEREOF FIELD OF THE INVENTION [0001]

The present invention relates to a wearable robot capable of variably controlling an impedance parameter for joint control based on a motion state, and a variable impedance control method thereof.

A wearing robot means a robot that is mounted on a human body and amplifies the strength of the arms and legs according to the wearer's intention to exercise, thereby increasing the physical ability of the human being.

In order for the wearing robot and the wearer to integrate and move naturally, and for stable walking at the time of initial contact, a spring-damper type impedance control based on the walking characteristics of a person is required.

However, existing worn robots were not designed for impedance control in various outdoor environments because they were developed to operate in indoor flat environment mainly for rehabilitation purpose. For this reason, conventional worn robots are limited in operation in outdoor environments such as military or disaster, such as slopes and stairs.

Accordingly, it is an object of the present invention to provide a wearable robot and its variable impedance control method which can be operated in consideration of impedance control for various outdoor environments.

It is another object of the present invention to provide a wearable robot and its variable impedance control method capable of variably controlling an impedance parameter (rigidity, damping, etc.) of a wearable robot based on a wearer's motion state.

According to an aspect of the present invention, there is provided a worn robot comprising: a sole link unit including a foot sensor and a tilt sensor, the foot link including a foot structure for the wearer to walk on; A foot link portion connected to the three-axis rotatable foot joint of the sole link portion to connect the knee joint; A femoral link portion connected to the unidirectionally rotatable knee joint of the lower link portion and including the joint driving portion; A backpack part connected to the femoral link part and connected to the hip joint on which the battery is mounted; And a sole sensor for detecting a walking state of the wearer and determining a motion state through estimation of the robot attitude using a sensor for measuring the inclination of the upper body and the sole of the wearer and controlling the impedance control parameter And a gait controller for controlling the joint drive unit by variably applying the gait controller.

The foot link portion may include a sensor capable of measuring the inclination of the ground during walking, and the lower link portion may include a sensor for converting at least one of an angle and an angular velocity of the ankle joint into an electrical signal.

And a force sensor capable of measuring force / torque information of the joint driving part, wherein the backpack part includes at least one of an angle and an angular velocity of the hip joint, A force sensor capable of measuring the force / torque information of the joint drive unit, and a sensor capable of measuring the inclination of the backpack unit.

The impedance control parameter includes a joint stiffness value calculated by a human body joint angle and a torque value obtained through a pre-human body movement according to a wearer's load, a walking speed, and a motion state; And a damping coefficient calculated based on the angular velocity and torque value of the human body joint.

The walking controller may variably apply the joint impedance value according to the parameter transition weight function of the hyperbola in order to minimize the system instability due to sudden parameter changes.

The walking control unit may generate a control command of the joint driving unit by applying the control parameter differently according to the wear weight or the angular velocity of the wearer's body when applying the impedance control parameter.

According to another aspect of the present invention, there is provided a method of controlling a variable impedance of a wearable robot, the method comprising: calculating a joint impedance value through a human body movement according to a wearer's load, a walking speed, ; Determining a walking state of the wearer with a sensor attached to the soles of the wearer robot; Determining a motion state through robot posture estimation using an upper body backpack part of the wearer robot and a tilt measurement sensor attached to the sole; And driving the joint driving part by variably applying the stored joint impedance value according to the determined gait state and motion state.

The joint impedance value is a joint stiffness value calculated by a human body joint angle and a torque value obtained through a human body movement according to a wearer's load, a walking speed, and a motion state; And a damping coefficient calculated based on the angular velocity and torque value of the human body joint.

The joint impedance value is variably applied according to a hyperbolic parameter transition weight function to minimize system instability due to a sudden change in impedance value.

When the joint impedance value is variably applied, the joint driving part can be driven by applying the control parameter differently according to the wearer's angular velocity or wearing weight of the wearer.

The wearable robot according to the present invention is capable of natural walking of a person even in an outdoor exercise environment such as a slope and a stair, and contributes to ensuring walking stability due to sudden force transmission during initial contact. In addition, by implementing a walking pattern similar to a human body, it is possible to increase the convenience of the wearer and minimize the damage of the human musculoskeletal system after wearing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a three-dimensional view showing a wear robot according to the present invention.
2 is a view showing the position of the sole sensor for determining the walking phase and the position sensor for measuring the sole of the sole.
3 is a view showing a walking control method of a wearing robot according to an embodiment of the present invention.
4 is an embodiment of a method for discriminating a walking step using a sole sensor attached to a soles of a sole.
5 is an example of kinematic-based posture estimation for determining the motion state.
6 is an exemplary view of various exercise conditions applied to the present invention.
7 is a flowchart showing a kinematic-based motion state discrimination method.
8 is a flowchart showing a variable impedance control method of a wearing robot according to an embodiment of the present invention.
9 to 11 are diagrams illustrating an example of a variable impedance control method according to an embodiment of the present invention,
12 is a diagram showing a method of deriving a variable impedance (joint stiffness value) according to a motion state.
13 is a graph showing a weight function applied to the present invention.

The present invention proposes a method of variably controlling the impedance parameters (stiffness, damping, etc.) of a wearing robot based on the motion state at the time of contact so that the robot can be used in military and disaster applications and can walk like a person.

The present invention preliminarily secures (stores) the joint impedance (stiffness, damping) values for the movement state, the movement (walking speed) and the transportation load from the walking characteristics of a person, And controls the wearing robot according to the determined motion state.

The walking stage of a person is determined using a sensor attached to the sole, and the motion state is calculated using an IMU (Inertial Measurement Unit) sensor (a posture sensor) attached to the robot and a joint angle sensor. By applying the control method of the present invention, it is possible to carry out continuous walking in a natural and stable manner in various environments even in a state in which the wearing robot is mounted.

The wearable robot according to the present invention plays a role of supporting a heavy load and allowing the wearer to walk without difficulty.

1 is a three-dimensional view of a wearable robot according to the present invention.

1, the wearable robot according to the present invention includes a walking control unit 100, a backpack unit 110 to which a battery is mounted, a hydraulic pressure supply unit 120, a right leg 130, And a leg portion 140.

The wearer robot includes a foot link unit including a foot sensor and a tilt sensor, a foot link unit connected to the three-axis rotatable foot joint of the foot link unit to connect the knee joint, The foot of the wearer is discriminated by using the femoral link part connected to the negative one-axis rotatable knee joint and the joint driving part, the backpack part connected to the hip joint to which the battery is attached and the sole sensor, A gait controller (100) for determining a motion state by estimating a robot posture using an upper body and a sole of a foot inclination sensor, and variably applying an impedance control parameter according to the determined gait state and a motion state, .

Each of the legs 130 and 140 is configured by connecting the pelvis link portion, the crotch link portion, the lower link portion, and the sole link portion to each other.

The wearer robot includes a joint angle sensor (hip joint pitch, knee joint pitch, ankle joint pitch) for measuring the angle of the joint, a force sensor (a hip joint drive force sensor, a knee joint drive force sensor) (IMU) for measuring the state of the foot and the posture sensor (IMU) (left and right) for measuring the tilted state of the ground contacting the sole, and a sole sensor (left and right) .

Fig. 2 shows the position of the sole sensor for determining the walking phase and the position sensor for measuring the sole of the sole.

As shown in FIG. 2, the sole sensor is composed of one or more force sensors (or pressure sensors) and is coupled to the bottom plate of the sole through the groove of the foot plate of the foot plate structure, and a flexible steel plate is inserted between the bottom plate and the bottom plate do. The posture sensor (IMU) is attached to the final structure of the foot joint composed of three-axis passive joints, and measures the tilt information of the sole.

3 shows a walking control method of a wearing robot according to an embodiment of the present invention.

3, the walking control unit 100 calculates the joint angle, the process driving force, and the walking distance measured from the sensors (joint angle sensor, force sensor, posture sensor and foot sensor) (S11, S12), the walking step and the movement state are discriminated based on the slope / force (IMU, GRF) of the sole and the foot, At this time, when the walking control is performed by compensating the gravity compensation, a joint torque is generated from the joint driving unit (S13).

The walking control unit 100 controls the walking step of the wearer such as an initial contact (IC), a stance (ST), a pre-swing (PW), a swing (SW) (Such as flat walking, uphill / downhill, uphill / downhill, etc.).

In this case, the initial grounding is a period in which the foot hoop is in contact with the floor, a stance period is a period in which the foot is touching the floor, a period in which the toe lifting is performed in order to shift the forehead to the forehead, Represents a period of time.

That is, the walking control unit 100 performs different walking control according to the four walking steps (transition) (IC, ST, PW, SW) and the flat, inclined upward / downward,

FIG. 4 is a view illustrating an example of a method of determining a walking step using a sole sensor attached to a top plate of a sole.

4, the walking control unit 100 includes four legs that are attached to four positions of the sole, that is, the inside of the toe foot inside, the outside of the foot, and the heel, (IC, ST, PW, SW) by combining the force sensor signal (GRF) (ground reaction force) detected from the four sole sensor sensors. The walking control unit 100 calculates a threshold value for discriminating the four walking steps

), And then the measured force sensor signals (GRF) and corresponding threshold values

), And judges On / Off of each walking step as shown in Table 1 below.

State x ₁ x ₂ x ₃ x ₄ Initial Grounding (IC) On Off Off Off The stance (ST) On On On On Dictionaries (PS) Off On On On Swing machine (SW) Off Off Off Off

5 is an example of kinematic-based posture estimation for determining a motion state.

The walking control unit 100 can calculate the ground contact angle with respect to the foot of the robot, that is, the foot, by using the kinematic analysis using the IMU of the upper body, the IMU of the sole of the foot, and the angle sensor information of each joint mounted on the wearing robot . The attitude of the robot may include a jump mode, a single support mode, and a double support mode.

The jump mode is estimated by a kinematic analysis of both feet based on the backpack as follows: the feet are off the ground.

Where T represents a 4x4 homogeneous transformation matrix,

Represent the angle from the back pack of the right leg to the hip, the hip angle, the knee angle and the ankle angle.

In the single support mode, only one foot touches the ground and is estimated by a kinematic analysis based on the foot touching the ground.

- When the left foot touches the ground.

- Your right foot touches the ground.

The double support mode is kinematically interpreted as a single support mode with both feet touching the ground and with respect to the leg behind the backpack coordinate system.

FIG. 6 is a diagram illustrating various motion states applied to the present invention, and FIG. 7 is a flowchart illustrating a kinematic motion state determination method.

As shown in FIG. 6, the wearer wears a wearing robot and can perform a flat walking, a slope climb, a down climb, a stair climb, and a stair climb.

The robot posture estimator (not shown) receives the joint angle and foot slope / force (IMU, GRF) from the joint angle sensor and the posture IMU and the sole sensor during walking of the wearer's foot of the walking control unit 100, A ground contact angle with respect to the foot contacting the ground is calculated (S100).

The robot posture estimator compares the vertical position of the sole of the trailing leg of the leading leg with the position of the sole of the leading leg at step S110 and compares the preceding leg with the leg following the leg at step S120. If the position of the preceding leg is higher than that of the leg following the comparison result, it is determined that the upward movement (stepped up or inclined up) is performed at step S130 and if it is lower, the downward motion is determined at step S140.

Then, in each of the steps S130 and S140, the calculated ground contact angle of the leg is compared with a threshold value of the ground angle, and if the ground contact angle of the following leg is larger than the ground threshold, If it is smaller than or equal to the predetermined value, it is determined that the stepping motion (descending) is performed (S150).

If there is no change in the output value of each sensor, the robot posture estimator determines that the previous motion is continuous.

8 is a flowchart illustrating a variable impedance control method of a wearable robot according to an embodiment of the present invention.

8, a joint impedance value (variable impedance control parameter) is calculated through a pre-human body movement according to the wearer's load, walking speed, and motion state in a state of wearing the wearable robot, and is stored in a memory (not shown) (S200). The joint impedance value is calculated based on the joint stiffness value and the human joint angular velocity and torque value calculated by the human body joint angle and torque value obtained through the pre-human body movement according to the wearer's load, walking speed, Lt; / RTI >

When the wearer actually walks with the wear robe, the gait controller 100 determines the walking state of the wearer based on the sensor attached to the soles of the wearer robot (S210). Then, the wearer's body backpack and the soles [0031] The motion state is estimated through the robot posture estimation using the inclination measuring sensor (S220).

Therefore, the walking control unit 100 variably applies the stored joint impedance values according to the determined walking state and the motion state to drive the joint driving unit (S230).

The gait control unit 100 generates a control command of the joint driving unit by applying the joint impedance value differently according to the weight of the walking controller 1000 or the wearer's body joint speed. Applying the joint impedance values according to the hyperbolic parameter transition weight function when applying the values minimizes system instability due to sudden parameter changes.

9 to 11 are diagrams illustrating an example of a variable impedance control method of a wearing robot according to an embodiment of the present invention.

Referring to FIG. 9, in the case of a flat walking, the walking controller 100 discriminates a walking step using a sole sensor, and variably controls an impedance parameter (stiffness, damping, etc.) according to the discriminated result. In Fig. 8, the walking step is divided into six stages (IC, LR, MS, TS, PS, and SW).

That is, the variable impedance control is performed in the initial contact (IC) step and the active control (ex, virtual torque control) based on the motion intention is performed in the stance unit ST including the steps LR, MS and TS Pre-transition is performed in the pre-excitation phase (PS), and reverse drive control is performed in the swash SW by zero impedance.

As shown in FIG. 10, in the case of stair walking, the variable impedance control is performed in the interval of Weight Acceptance (WA) as an initial striking point according to the following equation (1) Variable impedance control is performed during the initial contact (IC) interval.

[Equation 1]

Here, τ is the torque value, i is the joint, K is the joint stiffness value, B is the damping coefficient, θ is the sole of the sole and the mode is the motion state (ex, flat, step up / down, / Down).

FIG. 12 shows a method of deriving a variable impedance (joint stiffness value) according to a motion state, and FIG. 13 is a graph showing a weight function applied to the present invention.

Referring to FIG. 12, a joint stiffness (k) value is calculated based on a human body joint angle and a torque value through a human body movement according to a load, a speed, and a motion state, and damping b) Derive the coefficients and use them as control parameters.

In this case, the change of the parameter between the motion states minimizes the system instability according to the sudden change of the parameters by applying the weight function W (t) as shown in the following Equation 2.

&Quot; (2) "

Here, W (t) is a weighting function according to time, and a hyperbolic function can be applied as shown in the following equation and FIG.

As described above, the wearable robotic device according to the present invention can realize natural walking of a person even in an outdoor exercise environment such as an inclination or a stair, and contributes to ensuring gait stability due to abrupt force transmission during initial contact. In addition, the present invention realizes a walking pattern similar to a human body through a wearable robot, thereby enhancing the convenience of the wearer and minimizing the damage of the human musculoskeletal system after wearing.

It will be appreciated that the configurations and methods of the embodiments described above are not to be limited and that the embodiments may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Therefore, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive.

100: a walking control unit 110:
120: Hydraulic supply device 130: Right leg
140: left leg

Claims

1. A wearing robot for supporting a wearer's lower body to assist walking,
A sole link unit including a foot sensor and a tilt sensor, the foot link comprising a foot structure that the wearer can walk on and off;
A foot link portion connected to the three-axis rotatable foot joint of the sole link portion to connect the knee joint;
A femoral link portion connected to the unidirectionally rotatable knee joint of the lower link portion and including the joint driving portion;
A backpack part connected to the femoral link part and connected to the hip joint on which the battery is mounted; And
A foot sensor of the wearer to determine a walking state of the wearer and to determine a motion state by estimating a robot posture using a sensor for measuring the inclination of the wearer's upper body and foot so as to determine an impedance control parameter according to the determined walking state and motion state And a gait controller for variably controlling the joint drive unit,
Wherein the walking control unit variably applies joint impedance values according to a parameter transition weight function of a hyperbola in order to minimize system instability due to sudden parameter changes.

[2] The apparatus according to claim 1,
And a sensor capable of measuring the inclination of the ground during walking,
Wherein the lower link includes a sensor for converting at least one of an angle and an angular velocity of the ankle joint into an electric signal.

[2] The apparatus according to claim 1,
A sensor for converting at least one of angles and angular velocities of the knee joint into an electric signal, and a force sensor capable of measuring force / torque information of the joint drive part,
The backpack includes a sensor for converting at least one of an angle and an angular velocity of the hip joint into an electric signal, a force sensor capable of measuring force / torque information of the joint drive unit, and an angle sensor capable of measuring a tilt of the backpack. Not to wear robots.

The method of claim 1, wherein the impedance control parameter
The joint stiffness value calculated by the human body joint angle and torque value obtained through the pre-human body movement according to the wearer's load, walking speed, and exercise state; And
And a damping coefficient calculated based on the angular velocity of the human body joint and the torque value.

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2. The apparatus of claim 1, wherein the walking control unit
Wherein when the impedance control parameter is applied, the control command is generated by applying the control parameter differently according to the wearing weight or the angular velocity of the wearer's body joint.

Calculating and storing a joint impedance value through a pre-human body movement according to a wearer's load, a walking speed, and a motion state in a wearing state of the wearing robot;
Determining a walking state of the wearer with a sensor attached to the soles of the wearer robot;
Determining a motion state through robot posture estimation using an upper body backpack part of the wearer robot and a tilt measurement sensor attached to the sole; And
And driving the joint drive unit by variably applying the stored joint impedance value according to the determined gait state and motion state,
Wherein the joint impedance value is variably applied according to a hyperbolic parameter transition weight function to minimize system instability due to a sudden change in impedance value.

8. The method of claim 7, wherein the joint impedance value
The joint stiffness value calculated by the human body joint angle and torque value obtained through the pre-human body movement according to the wearer's load, walking speed, and exercise state; And
And a damping coefficient calculated based on a human body joint angular velocity and a torque value.

delete

The method of claim 7, wherein when the joint impedance value is variably applied, the joint driving unit is driven by applying control parameters differently according to the wearer's angular velocity or wear weight.