Master-Slave Robot Force Control for Controlled Separation

Solution Overview

Problem

In master-slave manipulators, the inability to operate the slave arm in a direction away from the work object without mode switching limits operability, as input to the master arm is disabled in contact mode, leading to potential damage and reduced control precision.

Innovation Solution

A robot system with a slave unit, master unit, and system controller that detects reaction and operating forces to generate operational commands, allowing the slave arm to move in a separating direction from the object while maintaining contact, thereby preventing damage and improving operability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the master-slave manipulator switches to contact mode when reaction force exceeds target force value, then the stability of control is improved, but the operability deteriorates because input to master arm is disabled and slave arm cannot be operated in separating direction

Engineering Contradiction:

Improvestability of controlVSAvoidoperability

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The system dynamically adjusts the control mode based on the direction of operator input. When the operator applies force in the pressing direction, force control is activated for stability. When the operator applies force in the separating direction, position control is activated to enable master arm operation. This dynamic switching resolves the contradiction by making the control system adaptive to different operational needs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control system changes the control parameters (control mode, gain values) based on the direction of the operating force relative to the reaction force. By detecting the angle between operating force and reaction force vectors, the system switches between force control and position control modes, thereby changing system parameters to simultaneously achieve stability in pressing direction and operability in separating direction.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If force control is applied in contact mode to maintain target force value, then the protection of workpiece and object is improved, but the ability to move slave arm in separating direction deteriorates

Engineering Contradiction:

Improvedamage preventionVSAvoidability to move slave arm

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The control system changes the control parameters (control mode, gain values) based on the direction of the operating force relative to the reaction force. By detecting the angle between operating force and reaction force vectors, the system switches between force control and position control modes, thereby changing system parameters to simultaneously achieve stability in pressing direction and operability in separating direction.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system continuously monitors the direction and magnitude of both reaction force and operating force, and uses this feedback to determine the appropriate control mode. When the operator applies force in the separating direction, the feedback mechanism triggers position control mode, enabling master arm operation while maintaining slave arm safety through controlled movement.

Inventive Principle:

Principle #23Feedback

3Stability of the object's composition

If mode switching operation is required to operate slave arm in separating direction, then the stability of force control is improved, but the productivity deteriorates due to additional operation steps

Engineering Contradiction:

Improveforce control stabilityVSAvoidoperational efficiency

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The system dynamically adjusts the control mode based on the direction of operator input. When the operator applies force in the pressing direction, force control is activated for stability. When the operator applies force in the separating direction, position control is activated to enable master arm operation. This dynamic switching resolves the contradiction by making the control system adaptive to different operational needs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system enables continuous operation without requiring explicit mode switching by the operator. The control mode changes automatically and continuously based on the real-time direction of the operating force, allowing the operator to seamlessly transition between pressing and separating operations without interrupting the workflow or reducing productivity.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS11478919B2Robot system and method of controlling the robot system

Publication Date: 2022.10.25 KAWASAKI JUKOGYO KK

AI summary

A robot system includes a slave unit including a slave-side force detector configured to detect a direction and a magnitude of a reaction force acting on a workpiece held by a work end of a slave arm, a master unit including a master-side force detector configured to detect a direction and a magnitude of an operating force applied by an operator to an operation end of a master arm, and a system controller configured to generate a slave operational command and a master operational command based on the operating force and the reaction force. The system controller includes a regulator configured to correct a moving direction of the work end so that the movement of the work end in a pressing direction of an object is regulated when the reaction force exceeds an acceptable value set beforehand.