ROBOT SYSTEM CONTROLLING METHOD, ROBOT SYSTEM, AND CONTROL APPARATUS FOR QUADRUPEDAL ROBOT

• US 20120072026A1
• Filed: 09/12/2011
• Published: 03/22/2012
• Est. Priority Date: 09/22/2010
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Takagi, Kiyoshi
• Granted Patent: US 8,958,915 B2
• Time in Patent Office: Days
• US Class Current: 700/261
• CPC Class Codes: B25J 9/1075 with muscles or tendons
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: B25J 9/1641 compensation for backlash, friction, compliance, elasticity in the joints
• CPC Class Codes: G05B 2219/39201 Control of joint stiffness
• CPC Class Codes: G05B 2219/39452 Select with mouse button a coordinate plane for micromanipulation
• CPC Class Codes: G05B 2219/39454 Rubber actuator, two muscle drive, one for extension other for traction
• CPC Class Codes: Y10S 901/01 Mobile robot
• CPC Class Codes: Y10S 901/09 Closed loop, sensor feedback controls arm movement

Abstract

An object of the present invention is to provide a robot system controlling method and robot system which perform link angle control and joint stiffness control through feedback control.

Claims

1. A robot system controlling method for a robot system which comprises a link whose base end is swingably supported by a fixing member, and a pair of actuators connected to the fixing member and the link and adapted to swing the link using a difference between contraction forces, adjusts the contraction forces of the actuators based on respective contraction force command values, and thereby controls operation of the link, the controlling method comprising:

performing a deviation calculation to calculate a value which represents a deviation between a swing angle θ

₁ and a target swing angle r_a of the link with respect to the fixing member;

performing torque command generation to perform PID control calculations on the value which represents the deviation and thereby generate a torque command value T₁ to swing the link;

performing multiplication to calculate a product U₁×

r of length r of a moment arm from a swing center of the link and a stiffness command value U₁ which represents a sum of the contraction force command values;

performing torque command correction to generate a new torque command value T₁ whose absolute value is limited to or below the product U₁×

r if the absolute value of the originally generated torque command value T₁ is larger than the product U₁×

r while using the originally generated torque command value T₁ as it is if the absolute value of the originally generated torque command value T₁ is equal to or smaller than the product U₁×

r; and

performing contraction force command value calculations to determine the contraction force command values using calculation formulae (U₁+T₁/r)/2, (U₁−

T₁/r)/2 based on the torque command value T₁ generated as a result of the torque command correction.

2. The robot system controlling method according to claim 1, wherein:

the robot system comprises a sensor adapted to generate a detection signal when an external force acts on the link; and

during a period when the detection signal continues to be output from the sensor, the deviation calculation multiplies the value which represents the deviation by 0 and thereby calculates a new value which represents the deviation.

12. The robot system controlling method according to claim 1, wherein a hyperbolic tangent function is used to limit the torque command correction.

3. A robot system controlling method for a robot system which comprises a first link whose base end is swingably supported by a fixing member, a second link whose base end is swingably supported at a tip of the first link, a pair of first actuators connected to the fixing member and the first link and adapted to swing the first link using a difference between contraction forces, a pair of second actuators connected to the first link and the second link and adapted to swing the second link using a difference between contraction forces, and a pair of third actuators connected to the fixing member and the second link and adapted to swing the first link and the second link using a difference between contraction forces, adjusts the contraction forces of the pair of first actuators, the pair of second actuators, and the pair of third actuators based on respective contraction force command values, and thereby controls operation of the first link and the second link, the controlling method comprising:

performing a first deviation calculation to calculate a value which represents a first deviation between a first swing angle θ

₁ and a first target swing angle r_a1 of the first link with respect to the fixing member;

performing first torque command generation to perform PID control calculations on the value which represents the first deviation and thereby generate a first torque command value T₁ needed to swing the first link;

performing a first multiplication to calculate a first product U₁×

r₁ of length r₁ of a moment arm from a swing center of the first link and a first stiffness command value U₁ which represents a sum of the contraction force command values for the first actuators;

performing a first torque command correction to generate a new first torque command value T₁ whose absolute value is limited to or below the first product U₁×

r₁ if the absolute value of the originally generated first torque command value T₁ is larger than the first product U₁×

r₁ while using the originally generated first torque command value T₁ as it is if the absolute value of the originally generated first torque command value T₁ is equal to or smaller than the first product U₁×

r₁;

performing first contraction force command value calculations to determine the contraction force command values for the first actuators using calculation formulae (U₁+T₁/r₁)/2, (U₁−

T₁/r₁)/2 based on the first torque command value T₁ generated as a result of the torque command correction;

performing a second deviation calculation to calculate a value which represents a second deviation between a second swing angle θ

₂ and a second target swing angle r_a2 of the second link with respect to the first link;

performing a second torque command generation to perform PID control calculations on the value which represents the second deviation and thereby generate a second torque command value T₂ to swing the second link;

performing a second multiplication to calculate a second product U₂×

r₂ of length r₂ of a moment arm from a swing center of the second link and a second stiffness command value U₂ which represents a sum of the contraction force command values for the second actuators;

performing a second torque command correction to generate a new second torque command value T₂ whose absolute value is limited to or below the second product U₂×

r₂ if the absolute value of the originally generated second torque command value T₂ is larger than the second product U₂×

r₂ while using the originally generated second torque command value T₂ as it is if the absolute value of the originally generated second torque command value T₂ is equal to or smaller than the second product U₂×

r₂; and

performing second contraction force command value calculations to determine the contraction force command values for the second actuators using calculation formulae (U₂+T₂/r₂)/2, (U₂−

T₂/r₂)/2 based on the second torque command value T₂.

4. The robot system controlling method according to claim 3, wherein:

the robot system comprises a sensor adapted to generate a detection signal when an external force acts on the second link;

during a period when the detection signal continues to be output from the sensor, the first deviation calculation multiplies the value which represents the first deviation by a first coefficient value G_t1 which represents 0 and thereby calculates a new value which represents the first deviation; and

during the period when the detection signal continues to be output from the sensor, the second deviation calculation multiplies the value which represents the second deviation by a second coefficient value G_t2 which represents 0 and thereby calculates a new value which represents the second deviation.

5. The robot system controlling method according to claim 4, further comprising:

performing third contraction force command value calculations to set the contraction force command values for the respective third actuators to ½

a third stiffness command value U₃ which represents a sum of the contraction force command values for the third actuators.

6. The robot system controlling method according to claim 3, wherein:

the robot system comprises a sensor adapted to generate a detection signal when an external force acts on the link;

during a period when the detection signal continues to be output from the sensor, the first deviation calculation multiplies the value which represents the first deviation by a first coefficient value G_t1 varied between 0 and 1 (both inclusive) and thereby calculates a new value which represents the first deviation; and

during the period when the detection signal continues to be output from the sensor, the second deviation calculation multiplies the value which represents the second deviation by a second coefficient value varied G_t2 between 0 and 1 (both inclusive) and thereby calculates a new value which represents the second deviation.

7. The robot system controlling method according to claim 6, wherein the first coefficient value G_t1 and the second coefficient value G_t2 are set to increase with passage of time from the start of the period when the detection signal continues to be output from the sensor.

8. The robot system controlling method according to claim 6, further comprising:

calculating a third stiffness command value U₃ which represents a sum of the contraction force command values for the third actuators using a calculation formula which includes the first stiffness command value U₁, the second stiffness command value U₂, the first target swing angle r_a1 and the second target swing angle r_a2 as variables, where the third stiffness command value U₃ is calculated so as to cause one of a major axis and a minor axis of an ellipse which represents stiffness characteristics which in turn represent magnitude of stiffness at a tip of the second link to be parallel to a reference axis in an orthogonal coordinate system defined in a plane in which the first link and the second link swing, the ellipse having a center at the tip of the second link in the orthogonal coordinate system; and

performing third contraction force command value calculations to set the contraction force command values for the respective third actuators to ½

the third stiffness command value U₃.

9. The robot system controlling method according to claim 4, wherein:

during the period when the detection signal continues to be output from the sensor, the first torque command generation adds a value obtained by multiplying results of the PID control calculations on the value which represents the first deviation existing just before the detection signal is output from the sensor by a value of (1−

G_t1) to a value obtained by multiplying results of the PID control calculations on the value which represents the first deviation by the first coefficient value G_t1, and thereby generates the first torque command value T₁; and

during the period when the detection signal continues to be output from the sensor, the second torque command generation adds a value obtained by multiplying results of the PID control calculations on the value which represents the second deviation existing just before the detection signal is output from the sensor by a value of (1−

G_t2) to a value obtained by multiplying results of the PID control calculations on the value which represents the second deviation by the second coefficient value G_t2, and thereby generates the second torque command value T₂.

10. A robot system controlling method for a robot system which comprises a link whose base end is swingably supported by a fixing member, a rotating motor placed at a joint between the fixing member and the link and adapted to swing the link, and a motor circuit configured such that the rotating motor will be regarded as a pair of virtual actuators adapted to swing the link using a difference between contraction forces, adjusts the contraction forces of the virtual actuators based on respective contraction force command values, and thereby controls operation of the link, the controlling method comprising:

performing a deviation calculation to calculate a value which represents a deviation between a swing angle θ

₁ and a target swing angle r_a of the link with respect to the fixing member;

performing torque command generation to perform PID control calculations on the value which represents the deviation and thereby generate a torque command value T₁ to swing the link;

performed multiplication to calculate a product U₁×

r of length r of a virtual moment arm from a swing center of the link and a stiffness command value U₁ which represents a sum of the contraction force command values;

performing torque command correction to generate a new torque command value T₁ whose absolute value is limited to or below the product U₁×

r if the absolute value of the torque command value T₁ generated in the torque command generation is larger than the product U₁×

r while using the torque command value T₁ generated in the torque command generation as it is if the absolute value of the torque command value T₁ generated in the torque command generation is equal to or smaller than the product U₁×

r; and

performing contraction force command value calculations to determine the contraction force command values using calculation formulae (U₁+T₁/r)/2, (U₁−

T₁/r)/2 based on the torque command value T₁ generated as a result of the torque command correction.

11. The robot system controlling method according to claim 10, wherein:

the robot system comprises a sensor adapted to generate a detection signal when an external force acts on the link;

during a period when the detection signal continues to be output from a sensor, the deviation calculation multiplies the value which represents the deviation by 0 and thereby calculates a new value which represents the deviation.

13. A robot system comprising:

a link whose base end is swingably supported by a fixing member;

a pair of actuators connected to the fixing member and the link and adapted to swing the link using a difference between contraction forces; and

a control apparatus adapted to adjust the contraction forces of the actuators based on respective contraction force command values and thereby control operation of the link, wherein

the control apparatus comprises;

a swing angle detection sensor adapted to detect a swing angle θ

₁ of the link with respect to the fixing member,

a deviation calculation unit adapted to calculate a value which represents a deviation between the swing angle θ

₁ and a target swing angle r_a,

a torque command generating unit adapted to perform PID control calculations on the value which represents the deviation and thereby generate a torque command value T₁ to swing the link,

a multiplication unit adapted to calculate a product U₁×

r of length r of a moment arm from a swing center of the link and a stiffness command value U₁ which represents a sum of the contraction force command values, a torque command correction unit adapted to output a new torque command value T₁ whose absolute value is limited to or below the product U₁×

r if the absolute value of the torque command value T₁ generated by the torque command generating unit is larger than the product U₁×

r while outputting the torque command value T₁ generated by the torque command generating unit as it is if the absolute value of the torque command value T₁ generated by the torque command generating unit is equal to or smaller than the product U₁×

r, and

a contraction force command value calculating unit adapted to determine the contraction force command values using calculation formulae (U₁+T₁/r)/2, (U₁−

T₁/r)/2 based on the torque command value T₁ output from the torque command correction unit.

14. The robot system according to claim 13 wherein:

the control apparatus further comprises a sensor adapted to generate a detection signal when an external force acts on the link; and

during a period when the detection signal continues to be output from a sensor, the deviation calculation unit multiplies the value which represents the deviation by 0 and thereby calculates a new value which represents the deviation.

24. A control apparatus for a quadrupedal robot comprising:

the robot system according to claim 13;

a table which determines the coefficient value G_t based on a leg phase of the quadrupedal robot and a detection signal of a sensor generated when an external force acts on the second link; and

a trajectory calculation unit adapted to recalculate the target swing angle at a specific time.

15. A robot system comprising:

a first link whose base end is swingably supported by a fixing member;

a second link whose base end is swingably supported at a tip of the first link;

a pair of first actuators connected to the fixing member and the first link and adapted to swing the first link using a difference between contraction forces;

a pair of second actuators connected to the first link and the second link and adapted to swing the second link using a difference between contraction forces;

a pair of third actuators connected to the fixing member and the second link and adapted to swing the first link and the second link using a difference between contraction forces; and

a control apparatus adapted to adjust the contraction forces of the pair of first actuators, the pair of second actuators, and the pair of third actuators based on respective contraction force command values, and thereby control operation of the first link and the second link, wherein

the control apparatus comprises;

a first swing angle detection sensor adapted to detect a first swing angle θ

₁ of the first link with respect to the fixing member,

a first deviation calculation unit adapted to calculate a value which represents a first deviation between the first swing angle θ

₁ and a first target swing angle r_a1,

a first torque command generating unit adapted to perform PID control calculations on the value which represents the first deviation and thereby generate a first torque command value T₁ to swing the first link,

a first multiplication unit adapted to calculate a first product U₁×

r₁ of length r₁ of a moment arm from a swing center of the first link and a first stiffness command value U₁ which represents a sum of the contraction force command values for the first actuators,

a first torque command correction unit adapted to output a new first torque command value T₁ whose absolute value is limited to or below the first product U₁×

r₁ if the absolute value of the first torque command value T₁ generated by the first torque command generating unit is larger than the first product U₁×

r₁ while outputting the first torque command value T₁ generated by the first torque command generating unit as it is if the absolute value of the first torque command value T₁ generated by the first torque command generating unit is equal to or smaller than the first product U₁×

r₁,

a first contraction force command value calculating unit adapted to determine the contraction force command values for the first actuators using calculation formulae (U₁+T₁/r₁)/2, (U₁−

T₁/r₁)/2 based on the first torque command value T₁ output from the first torque command correction unit,

a second swing angle detection sensor adapted to detect a second swing angle θ

₂ of the second link with respect to the first link,

a second deviation calculation unit adapted to calculate a value which represents a second deviation between the second swing angle θ

₂ and a second target swing angle r_a2,

a second torque command generating unit adapted to perform PID control calculations on the value which represents the second deviation and thereby generate a second torque command value T₂ to swing the second link,

a second multiplication unit adapted to calculate a second product U₂×

r₂ of length r₂ of a moment arm from a swing center of the second link and a second stiffness command value U₂ which represents a sum of the contraction force command values for the second actuators,

a second torque command correction unit adapted to output a new second torque command value T₂ whose absolute value is limited to or below the second product U₂×

r₂ if the absolute value of the second torque command value T₂ generated by the second torque command generating unit is larger than the second product U₂×

r₂ while outputting the second torque command value T₁ generated by the second torque command generating unit as it is if the absolute value of the second torque command value T₂ generated by the second torque command generating unit is equal to or smaller than the second product U₂×

r₂, and

a second contraction force command value calculating unit adapted to determine the contraction force command values for the second actuators using calculation formulae (U₂+T₂/r₂)/2, (U₂−

T₂/r₂)/2 based on the second torque command value T₂ output from the second torque command correction unit.

16. The robot system according to claim 15 wherein:

the control apparatus further comprises a sensor adapted to generate a detection signal when an external force acts on the second link;

during a period when the detection signal continues to be output from the sensor, the first deviation calculation unit multiplies the value which represents the first deviation by a first coefficient value G_t1 which represents 0 and thereby calculates a new value which represents the first deviation; and

during a period when the detection signal continues to be output from the sensor, the second deviation calculation unit multiplies the value which represents the second deviation by a second coefficient value G_t2 which represents 0 and thereby calculates a new value which represents the second deviation.

17. The robot system according to claim 16 further comprising a third contraction force command value calculating unit adapted to set the contraction force command values for the respective third actuators to ½

a third stiffness command value U₃ which represents a sum of the contraction force command values for the third actuators.

18. The robot system according to claim 15 wherein:

the control apparatus further comprises a sensor adapted to generate a detection signal when an external force acts on the link;

during a period when the detection signal continues to be output from the sensor, the first deviation calculation unit multiplies the value which represents the first deviation by a first coefficient value G_t1 varied between 0 and 1 (both inclusive) and thereby calculates a new value which represents the first deviation; and

during the period when the detection signal continues to be output from the sensor, the second deviation calculation unit multiplies the value which represents the second deviation by a second coefficient value varied G_{t2 between} 0 and 1 (both inclusive) and thereby calculates a new value which represents the second deviation.

19. The robot system according to claim 18 wherein the first coefficient value G_t1 and the second coefficient value G_t2 are set to increase with passage of time from the start of the period when the detection signal continues to be output from the sensor.

20. The robot system according to claim 18 further comprising:

a calculating unit adapted to calculate a third stiffness command value U₃ which represents a sum of the contraction force command values for the third actuators using a calculation formula which includes the first stiffness command value U₁, the second stiffness command value U₂, the first target swing angle r_a1 and the second target swing angle r_a2 as variables, where the third stiffness command value U₃ is calculated so as to cause one of a major axis and a minor axis of an ellipse which represents stiffness characteristics which in turn represent magnitude of stiffness at a tip of the second link to be parallel to a reference axis in an orthogonal coordinate system defined in a plane in which the first link and the second link swing, the ellipse having a center at the tip of the second link in the orthogonal coordinate system; and

a third contraction force command value calculating unit adapted to set the contraction force command values for the respective third actuators to ½

the third stiffness command value U₃.

21. The robot system according to claim 16 wherein:

during the period when the detection signal continues to be output from the sensor, the first torque command generating unit adds a value obtained by multiplying results of the PID control calculations on the value which represents the first deviation existing just before the detection signal is output from the sensor by a value of (1−

G_t1) to a value obtained by multiplying results of the PID control calculations on the value which, being calculated by the first deviation calculation unit, represents the first deviation by the first coefficient value G_t1 and thereby generates the first torque command value T₁; and

during the period when the detection signal continues to be output from the sensor, the second torque command generating unit adds a value obtained by multiplying results of the PID control calculations on the value which represents the second deviation existing just before the detection signal is output from the sensor by a value of (1−

G_t2) to a value obtained by multiplying results of the PID control calculations on the value which, being calculated by the second deviation calculation unit, represents the second deviation by the second coefficient value G_t2, and thereby generates the second torque command value T₂.

22. A robot system comprising:

a link whose base end is swingably supported by a fixing member;

a rotating motor placed at a joint between the fixing member and the link and adapted to swing the link;

a motor circuit configured such that the rotating motor will be regarded as a pair of virtual actuators adapted to swing the link using a difference between contraction forces; and

a control apparatus adapted to adjust the contraction forces of the virtual actuators based on respective contraction force command values and thereby control operation of the link, wherein

the control apparatus comprises;

a deviation calculation unit adapted to calculate a value which represents a deviation between a swing angle θ

₁ and a target swing angle r_a of the link with respect to the fixing member;

a torque command generation unit adapted to perform PID control calculations on the value which represents the deviation and thereby generate a torque command value T₁ to swing the link;

a multiplication unit adapted to calculate a product U₁×

r of length r of a virtual moment arm from a swing center of the link and a stiffness command value U₁ which represents a sum of the contraction force command values,

a torque command correction unit adapted to output a new torque command value T₁ whose absolute value is limited to or below the product U₁×

r if the absolute value of the torque command value T₁ generated by the torque command generating unit is larger than the product U₁×

r while outputting the torque command value T₁ generated by the torque command generating unit as it is if the absolute value of the torque command value T₁ generated by the torque command generating unit is equal to or smaller than the product U₁×

r, and

a contraction force command value calculating unit adapted to determine the contraction force command values using calculation formulae (U₁+T₁/r)/2, (U₁−

T₁/r)/2 based on the torque command value T1 output from the torque command correction unit.

23. The robot system according to claim 22 wherein:

the control apparatus further comprises a sensor adapted to generate a detection signal when an external force acts on the link; and

during a period when the detection signal continues to be output from a sensor, the deviation calculation unit multiplies the value which represents the deviation by 0 and thereby calculates a new value which represents the deviation.