Robot Force Feedback Using Velocity-Based Virtual Reaction
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Solution Overview
Problem
Conventional robot systems face challenges in maintaining high precision during operations, as the master arm unintentionally moves when the operator removes their hand, leading to decreased work accuracy, especially in applications requiring high precision like component fitting and surgical operations.
Innovation Solution
A robot system that includes a virtual reaction-force information generating module, which outputs force information proportional to the velocity of the end effector, allowing the operator to perceive a virtual reaction force, thereby maintaining control and precision without unintended movement of the operating part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If force feedback from the slave arm is presented to the master arm, then the operator can perceive the interaction force with the object, but the master arm moves unintentionally when the operator removes their hand, decreasing work accuracy
Solution Approach 1:
The patent introduces a virtual reaction force as an intermediary between the actual contact force and the feedback to the operator. Instead of directly transmitting the slave arm's contact force to the master arm, a virtual force with viscous resistance characteristics is generated based on velocity detection. This mediator prevents direct coupling that causes unintended movement while maintaining operator perception of interaction.
Solution Approach 2:
The patent changes the parameter basis for force feedback from position-based actual contact force to velocity-based virtual reaction force. By detecting the velocity of the end effector and generating a virtual force proportional to this velocity with viscous resistance characteristics, the system transforms the feedback mechanism to eliminate instability while preserving operational awareness.
2Manufacturing precision
If virtual reaction force with viscous resistance is applied to the master arm, then work accuracy is improved, but the system complexity increases due to velocity detection and virtual force generation
Solution Approach 1:
The master arm's actuator serves multiple functions: it controls the position of the master arm for normal operation and simultaneously generates the virtual reaction force with viscous resistance. This multi-functionality reduces the need for separate force feedback actuators, thereby limiting the increase in system complexity while achieving improved work accuracy.
3Loss of information
If the force feedback is based on actual contact force, then the operator perceives real interaction, but the master arm stability deteriorates when the operator releases the operating part
Solution Approach 1:
The patent transitions from a static force feedback model (based on contact force) to a dynamic model where the virtual reaction force depends on the velocity of the end effector. The viscous resistance characteristic means the force is proportional to velocity, automatically adapting to the operational state: providing resistance during movement and becoming zero at rest, thus maintaining stability when the operator releases the master arm.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables highly precise operations by allowing operators to maintain control and perception of virtual reaction forces, preventing unintentional movement and improving work accuracy in high-precision tasks.
Implementation Method 1
a velocity detector configured to detect a velocity at a tip end of the end effector
Data Source
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AI summary
A robot system is provided, which includes a robot body including a robot arm and an end effector attached to the robot arm, an operating device, having an operating part and configured to output, when the operating part is operated, operational information according to the operation, a motion controller configured to control operation of the robot body according to the operational information outputted from the operating device, a velocity detector configured to detect a velocity at a tip end of the end effector, a virtual reaction-force information generating module configured to output force information containing a first force component having a positive correlation to the velocity at the tip end of the end effector, as virtual reaction-force information, and a force applying device configured to give a force to the operating part in order to make an operator perceive a force according to the virtual reaction-force information outputted from the virtual reaction-force information generating module.