# US 12,109,702 B2 · Method of adjusting force control parameter, robot system, and force control parameter adjustment program

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- Number: US 12,109,702 B2
- Document ID: US12109702B2
- Status: Granted
- Kind: B2
- Application number: 17/472,779
- Filed: 2021-09-13
- Published: 2022-03-17
- Granted: 2024-10-08
- Earliest claimed: 2020-09-14
- Assignees: Seiko Epson Corporation
- Applicants: Seiko Epson Corporation
- Inventors: Yasuhiro Shimodaira
- Web page: https://patentgrep.com/patent/US12109702B2

## CPC

- B25J 9/163: {learning, adaptive, model based, rule based expert control}
- B25J 9/1612: {characterised by the hand, wrist, grip control}
- B25J 9/1633: {compliant, force, torque control, e.g. combined with position control}
- B25J 9/1687: {Assembly, peg and hole, palletising, straight line, weaving pattern movement}
- G05B 19/4155: characterised by program execution, i.e. part program or machine function execution, e.g. selection of a program
- G05B 2219/39322: Force and position control
- G05B 2219/40032: Peg and hole insertion, mating and joining, remote center compliance
- G05B 2219/40269: Naturally compliant robot arm
- B25J: MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES ({manipulators specially adapted for use in surgery A61B34/70; manipulators used in cleaning hollow articles B08B9/04}; manipulators associated with rolling mills B21B39/20; manipulators associated with forging machines B21J13/10; {manipulators associated with picking-up and placing mechanisms B23P19/007}; means for holding wheels or parts thereof B60B30/00; {vehicles with ground-engaging propulsion means, e.g. walking members B62D57/02, B62D57/032; devices for picking-up and depositing articles or materials between conveyors B65G47/90, B65G47/91; manipulators with gripping or holding means for transferring packages B65H67/065}; cranes B66C; {manipulators used in the protection or supervision of pipe-line installations F17D5/00; walking equipment adapted for nuclear steam-generators F22B37/006}; manipulators specially adapted for, or associated with, nuclear reactors G21C; {apparatus used for handling wafers during manufacture or treatment of semiconductor H10P72/50})
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)

## Abstract

A first step of executing a first operation to bring a hand placed on a robot arm or a first object held by the hand into contact with a second object based on a first force control parameter, a second step of acquiring information of an external force applied to the robot arm by executing a second operation different from the first operation on a robot with the hand or the first object in contact with the second object, a third step of acquiring information of external rigidity based on the acquired external force information, and a fourth step of changing the force control parameter from the first force control parameter to a second force control parameter acquired based on the acquired external rigidity information and a position of a control point corresponding to the acquired external rigidity information are provided.

## Claims

### Claim 1

A method for causing a processor to execute a process, the method comprising executing on the processor the steps of:
executing a first operation to bring a first object held by a hand of a robot arm of a robot into contact with a second object based on a first force control parameter for a force sensor, a tool center point being set on the hand;
detecting a contact state between the first object and the second object;
detecting a first position of the tool center point when the processor detects the contact state;
acquiring an external force value applied to the robot arm by executing a second operation different from the first operation on the robot with the hand, the first object being further pushed toward the second object while the first and second objects are in the contact state in the second operation;
detecting a second position of the tool center point when the processor ends the second operation;
acquiring information of external rigidity based on a function of the acquired external force value and a movement amount of the tool center point between the first and second positions; and
changing the first force control parameter to a second force control parameter based on the acquired information of the external rigidity,
wherein the second operation includes an operation to drive the robot arm to move the first object in first directions crossing second directions along which the first object is inserted into and pulled out from the second object.

### Claim 2 (depends on 1)

The method according to claim 1, wherein
an element determining the external rigidity includes information of an element belonging to the robot arm, information of an element belonging to the hand, information of an element belonging to the first object, and information of an element belonging to the second object.

### Claim 3 (depends on 1)

The method according to claim 1, wherein
the second operation is executed by driving of the robot arm by position control.

### Claim 4 (depends on 1)

The method according to claim 1, wherein
in the second operation, the tool center point is moved in at least one direction of an insertion direction in which the first object is inserted into the second object, a direction crossing the insertion direction, and a rotation direction rotating about an axis along the insertion direction.

### Claim 5 (depends on 1)

The method according to claim 1, wherein
in the acquiring of the external force value, the movement amount of the tool center point is increased until the detected external force value reaches a predetermined value.

### Claim 6 (depends on 1)

The method according to claim 1, wherein
the second force control parameter is further adjusted based on information of a type of the hand and information of a type of the first object.

### Claim 7

A robot system comprising:
a robot having a robot arm driven by force control and performing work;
a force sensor configured to detect a force applied to the robot arm;
a memory configured to store a program; and
a processor configured to execute the program so as to:
perform a first operation to bring a first object held by a hand of the robot arm into contact with a second object based on a first force control parameter for the force sensor, a tool center point being set on the hand;
detect a contact state between the first object and the second object;
detect a first position of the tool center point when the processor detects the contact state;
acquire an external force value of the force applied to the robot arm by executing a second operation different from the first operation on the robot with the hand, the first object being further pushed toward the second object while the first and second objects are in the contact state in the second operation;
detect a second position of the tool center point when the processor ends the second operation;
acquire information of external rigidity based on a function of the acquired external force value and a movement amount of the tool center point between the first and second positions; and
change the first force control parameter to a second force control parameter based on the acquired information of the external rigidity,
wherein the second operation includes an operation to drive the robot arm to move the first object in first directions crossing second directions along which the first object is inserted into and pulled out from the second object.

### Claim 8 (depends on 7)

The robot system according to claim 7, wherein
the force sensor is configured to detect the force when the robot arm is driven by the force control.

### Claim 9

A non-transitory computer-readable storage medium storing a force control parameter adjustment program for causing a computer to execute a process by a processor so as to perform the steps of:
executing a first operation to bring a first object held by a hand of a robot arm of a robot into contact with a second object based on a first force control parameter for a force sensor, a tool center point being set on the hand;
detecting a contact state between the first object and the second object;
detecting a first position of the tool center point when the processor detects the contact state;
acquiring an external force value applied to the robot arm by executing a second operation different from the first operation on the robot with the hand, the first object being further pushed toward the second object while the first and second objects are in the contact state in the second operation;
detecting a second position of the tool center point when the processor ends the second operation;
acquiring information of external rigidity based on a function of the acquired external force value and a movement amount of the tool center point between the first and second positions; and
changing the first force control parameter to a second force control parameter based on the acquired information of the external rigidity,
wherein the second operation includes an operation to drive the robot arm to move the first object in first directions crossing second directions along which the first object is inserted into and pulled out from the second object.