Balancer and controlling method thereof

• US 4,640,663 A
• Filed: 12/02/1983
• Issued: 02/03/1987
• Est. Priority Date: 12/13/1982
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kikuchi, Hiroshi, Niinomi, Tatsuya
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/557,430
• Time in Patent Office: 1,159 Days
• Field of Search: 414/5, 414/730, 414/719, 901/5, 901/9, 901/48, 901/49, 901/6, 901/8, 901/45
• US Class Current: 414/730
• CPC Class Codes: B25J 13/085 Force or torque sensors B25J13/082, B25J13/084 take precedence
• CPC Class Codes: B25J 19/0004 Braking devices brakes in general F16D
• CPC Class Codes: B25J 19/0008 Balancing devices
• CPC Class Codes: B25J 19/063 working only upon contact with an outside object

Abstract

A robot balancer (2) and a method for controlling the balancer is disclosed which has a step or a force sensor (10) mounted on the tip of the arm (3) of the balancer (2), a step or an operational means (21) for calculating the velocity of the balancer from the force given by the force sensor, and a step or a control means (15) for controlling a velocity of the balancer (2) in response to a signal from the force sensor.

Claims

1. A method of controlling a balancer, comprising the steps of:

receiving a first instruction for controlling movement in a vertical direction of the arm of a balancer;

moving said arm according to said first instruction while the distal end of said arm is subjected to external forces;

detecting a force added to the arm along said vertical direction with a force sensor mounted on the distal end portion of the arm;

determining a velocity instruction for the balancer in response to the first signal and directing the distal end of the balancer to follow movement indicated by said external forces by modifying said velocity instruction with a second signal derived from the force sensor; and

applying said velocity instruction to control the velocity of the balancer.

2. The method of claim 1, further comprising the steps of activating a brake to stop movement of the balancer when the force sensor detects a force larger than a predetermined value.

5. A balancer, comprising:

a base;

an arm member pivotally mounted on said base to hold an article;

means for receiving a first instruction directing movement of said arm member in a vertical direction;

drive means for actively moving said arm member in response to said first instruction;

a sensor suitable for being grasped and actively moved by forces external to said drive means, mounted on the end portion of said arm for detecting a force added vertically to said arm by said external forces while said sensor is grasped and for generating a signal having a value proportional to the value of the force detected; and

control means for determining a velocity instruction for said arm member from said first instruction and minimizing the magnitude of said added force by modifying said first instruction in response to the signal generated by said force sensor and applying the velocity instruction to control said drive means.

3. The balancer of claim 5, wherein said control means includes a velocity calculator for generating said velocity instruction in response to reception of said first instruction for the balancer from a robot and said signal from said force sensor.

4. The balancer of claim 3, further comprising:

a force calculator for detecting an overload at the junction between said balancer and the robot by comparing said signal to a predetermined value, and for generating an overload signal when said signal exceeds said predetermined value;

a brake for stopping said drive means; and

a drive circuit coupled to said velocity calculator and said force calculator for operating said drive means in response to reception of the velocity instruction sent from said velocity calculator, and for activating said break in response to reception of said overload signal.

6. The balancer of claim 5, wherein said sensor includes graspable means for forming a connection to a robot and said sensor is interposed between said graspable means and said arm for sensing said added force.

7. The balancer of claim 5, wherein said force sensor includes a strain gauge and a plate, said strain gauge being fixed on said plate.

8. The balancer of claim 5, wherein said force sensor includes four strain gauges and two plates, and each of said strain gauges is fixed on the both sides of the plates.

9. The balancer of claim 5, further comprising:

means connected to said force sensor and graspable by a robot when the balancer is operated in cooperation with said robot, for forming a junction between said robot and said arm member.

10. The balancer of claim 5, wherein said control means has safety means connected with the force sensor to receive said signal, for detecting a force added to the arm whereby said safety means is able to control said drive means and the balancer is stopped when the force sensor detects a force larger than a predetermined value.

11. A balancer operable in cooperation with a robot, comprising:

a base;

an arm member pivotally mounted on said base to hold an article;

drive means for moving said arm member;

a force sensor mounted on the end portion of said arm for detecting a force added vertically to said arm by the robot and for generating a signal representative of the magnitude of said force;

means connected to said arm by said force sensor for forming a junction with the robot; and

means of controlling said drive means, including;

a velocity calculator for receiving a velocity signal from the robot for directing movement of said arm in a vertical direction, and a force signal from said force sensor, and for determining and applying to said drive means a velocity instruction for minimizing the magnitude of said vertically added force while following movement of the robot in response to reception of said force signal by modifying the value of said velocity instruction;

a force calculator for detecting an overload at said junction by comparing said force signal to a predetermined value and for generating an overload signal when the value of said signal exceeds said predetermined value;

a brake for stopping said drive means;

a drive circuit coupled to said velocity calculator and said force calculator for operating said drive means in response to reception of the velocity signal sent from said velocity calculator and for activating said brake in response to reception of said overload signal.

12. The balancer of claim 11, wherein said force sensor separates said junction forming means from said arm.

13. The balancer of claim 12, wherein said force sensor further comprises:

a plurality of horizontally disposed members having spaced apart proximal ends attached to said arm;

means for joining the distal ends of said members; and

means positioned on opposite horizontal surfaces of said members for sensing deformation of said horizontal members.

14. The balancer of claim 13, wherein said junction forming means is attached to said joining means.

15. A balancer operable in cooperation with a robot, comprising:

a base;

an arm member pivotally mounted on said base to hold an article;

drive means for moving said arm member;

means for receiving a first instruction for directing movement of said arm member by said drive means;

control means for determining a velocity instruction for said arm member from said first instruction and for applying the velocity instruction to control said drive means; and

a sensor suitable for being grasped, mounted on the distal end portion of said arm for detecting a force added vertically to said arm while said sensor is grasped and for providing to said control means a signal having a value proportional to the value of the force detected;

whereby said control means determines a corrected velocity instruction for said arm member from the first instruction and the signal generated by said force sensor and applies the corrected velocity instruction to control said drive means.

16. The balancer of claim 15, wherein said control means includes a velocity calculator for receiving said first instruction for the balancer from the robot and the signal from said sensor, and for determining and applying said corrected velocity instruction to said drive means in response to a reception of said first instruction and said signal.

17. The balancer of claim 16, further comprising:

force calculator means for detecting an overload at the junction between the robot and said sensor while said sensor is grasped by the robot, for detecting an overload at said junction by comparing said signal to a predetermined value and for generating an overload signal when the value of said signal exceeds said predetermined value;

a break for stopping said drive means; and

a drive circuit coupled to said velocity calculator and said force calculator means for operating said drive means in response to reception of the corrected velocity instruction sent from said velocity calculator means, and for activating said break in response to reception of said overload signal.

18. A balancer operable in cooperation with a robot, comprising:

arm means having one extremity providing a first terminus pivotally connectable to a base and a second extremity forming a distal terminus portion, for holding an article;

drive means for moving said arm means;

graspable sensor means mounted at said distal terminus portion, for responding to force added to said arm means while said sensor is grapsed by the robot, by generating a correction signal having a value proportional to the value of one component of the force added to said arm means; and

control means for receiving an electrical signal providing a first instruction and causing said drive means to move said arm in response to said first instruction, and generating a corrected instruction for controlling said drive means in response to reception of said electrical signal and said correction signal.

19. The balancer of claim 18, wherein said control means includes a velocity calculator for receiving the electrical signal from the robot and the correction signal from said sensor means, and for determining and applying said correction signal to said drive means in response to reception of said electrical signal and said correction signal.

20. The balancer of claim 19, further comprising:

a force calculator for detecting an overload at the junction between the robot and said sensor means by comparing said correction signal to a predetermined value, and for generating an overload signal when the value of said correction signal exceeds said predetermined value;

a brake for stopping said drive means; and

a drive circuit coupled to said velocity calculator and said force calculator for operating said drive means in response to reception of the corrected instruction, and for activating said brake in response to reception of said overload signal.