Control unit for a multi-degree-of freedom manipulator

• US 4,989,161 A
• Filed: 02/29/1988
• Issued: 01/29/1991
• Est. Priority Date: 02/27/1987
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Oaki, Junji
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): Gordon, Paul
• Application Number:
  US07/161,760
• Time in Patent Office: 1,065 Days
• Field of Search: 364/513, 364/474.12, 364/167.01, 364/513, 318/561, 318/568, 318/632, 901/20, 901/23, 901/9
• US Class Current: 700/261
• CPC Class Codes: B25J 9/1641 compensation for backlash, friction, compliance, elasticity in the joints
• CPC Class Codes: G05B 2219/37356 Torsion, twist
• CPC Class Codes: G05B 2219/39186 Flexible joint
• CPC Class Codes: G05B 2219/40599 Force, torque sensor integrated in joint

Abstract

A control unit for a multi-degree-of-freedom manipulator comprising a torque sensor for detecting the force exerting on each joint shaft and operational means for adding first and second correction values to the input signals to the motor actuator in accordance with the torque signal produced from the torque sensor. With this construction, non-linear and interference forces as well as effects due to the low rigidity of the joints can be removed without identifications of the link or arm parameters, and a striking improvement of the control performance can be achieved.

Claims

1. A control unit for a multi-degree-of-freedom manipulator and having a motor link system including a motor for producing an output torque at each joint shaft actuator and a motor rotational angle position control system, which further comprises:

a non-linear and interference force compensation control system having a torque sensor for detecting a torque (τ

) exerting on each joint shaft and a first operator;

a flexure and vibration compensation control system having a second operator,

a first correction value being produced through said first operator which multiplies a torque signal (τ

) produced from the torque sensor by a reciprocal of a reduction gear ratio (1/N),

a second correction value being produced through said second operator which multiplies the torque signal (τ

) produced from the torque sensor by a reciprocal of a spring constant (1/KG) of each joint; and

operational means for adding the first and second correction values to input signals to the motor actuator.

2. The control unit for a multi-degree-of-freedom manipulator as claimed in claim 1 wherein said flexure and vibration compensation control system further comprises a third operator (F2) for producing an operational signal in accordance with the second correction value, an adder for adding a target value of a link angle (θ

er) and the second correction value as an actual twist angle (e), and a fourth operator for producing a target value of the motor angle (θ

mr) multiplied by the reduction gear ratio of N.

3. The control unit for multi-degree-of-freedom manipulator as claimed in claim 2 wherein said third operator F2 is a PID functional operator.

4. The control unit for a multi-degree-of-freedom manipulator as claimed in claim 1 wherein said motor rotational angle position control system comprises an angle sensor for detecting an actual rotational angle (θ

m) of the motor actuator and a second adder for adding a target value of the motor angle and an actual motor rotational angle signal from the angle sensor.

5. The control unit for a multi-degree-of-freedom manipulator as claimed in claim 4 wherein said operational means comprises a third adder for adding an output signal from the second adder and said first and second correction values.

6. The control unit for a multi-degree-of-freedom manipulator as claimed in claim 5 wherein said motor link system further comprises a fourth adder for adding an output signal from the third adder and a feedback signal of (-τ

/N).

7. A control unit for a multi-degree-of-freedom manipulator, comprising:

a motor;

a reduction gear; and

a link;

said control unit comprising;

a torque sensor for detecting any torque exerted upon the input of said link;

a means connected to said torque sensor for multiplying any torque detected by said torque sensor by the reciprocal number of the reduction ratio of said reduction gear; and

a means connected to said multiplying means for increasing the input signal to said motor by the torque multiplied by the reciprocal number of the reduction ratio.

8. A control unit for a multi-degree-of-freedom manipulator having a motor actuator by which an output torque is produced through each joint shaft, which comprises:

torque sensing means for detecting the force exerted on each joint shaft; and

operational means for adding first and second correction values to input signals to the motor actuator in accordance with a torque signal produced from said torque sensing means.

wherein the first correction value to be applied to one input of the operational means is equal to the torque signal divided by the reduction gear ratio of the motor actuator side.

9. A control unit for a multi-degree-of-freedom manipulator having a motor actuator by which an output torque is produced through each joint shaft, which comprises:

torque sensing means for detecting the force exerted on each joint shaft; and

operation means for adding first and second correction values to input signals to the motor actuator in accordance with a torque signal produced from said torque sensing means;

wherein

the second correction value to be applied to an input of the operational means is equal to the torque signal divided by a reduction gear ratio of the motor actuator side.