Robot Cable Reactive Force Compensation for Precision Control
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Solution Overview
Problem
Current multi-joint robots lack precision in controlling forces of several grams due to reactive forces generated by wire members, which interfere with torque measurements and limit their applicability in assembling lightweight components, necessitating dedicated apparatuses that increase production costs and prolong start-up periods.
Innovation Solution
A robot apparatus with a sensor system that measures and compensates for reactive forces applied by wire members, allowing precise control of joints by subtracting these forces from torque sensor outputs, enabling high-precision force control without the need for dedicated equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wire members are used to transmit driving signals between robot units, then the robot structure becomes simpler and more general-purpose, but reactive forces generated by wire member deformation interfere with torque measurements and reduce force control precision
Solution Approach 1:
The patent extracts and separates the harmful reactive force from the useful torque measurement by introducing a dedicated sensor (cable reactive force measuring unit) that measures only the cable reactive force. This allows the controller to subtract the measured reactive force from the total torque sensor output, obtaining the accurate useful torque for force control.
Solution Approach 2:
The patent introduces an intermediary measurement system (cable reactive force measuring unit with sensor) that acts as a mediator between the wire member and the control system. This intermediary device measures the reactive force generated by wire member deformation and provides correction data to the controller, enabling precise force control despite the presence of wire members.
2Reliability
If torque sensors are arranged in joints to measure torque, then force control capability is improved, but reactive forces from deformed wire members create measurement errors that reduce precision for lightweight component assembly
Solution Approach 1:
The patent extracts the harmful reactive force component from the torque sensor measurement by using a separate cable reactive force measuring unit. This unit specifically measures only the reactive force portion, allowing the controller to subtract it from the total torque measurement and obtain the accurate useful torque for lightweight component assembly.
Solution Approach 2:
The patent implements a feedback mechanism where the cable reactive force measuring unit continuously measures the reactive force and feeds this information back to the controller. The controller then compensates for this reactive force in real-time, maintaining accurate torque measurements even when wire members are deformed during robot operation.
3Measurement precision
If dedicated apparatuses are used for assembling lightweight components, then force control precision is sufficient, but production costs increase and start-up periods are prolonged
Solution Approach 1:
The patent makes the robot apparatus universal by enabling it to handle both heavy and lightweight components with the same system. By adding the cable reactive force measuring unit and implementing the correction algorithm, the same robot can precisely control forces for lightweight component assembly without requiring dedicated apparatuses, thereby reducing production costs and start-up periods.
Solution Approach 2:
The patent changes the control parameter by introducing reactive force measurement and correction. Instead of requiring different apparatuses for different weight ranges, the system dynamically adjusts the torque control by subtracting the measured reactive force, allowing the same robot to precisely control forces across a wide range of component weights.
Data Source
AI summary
A robot apparatus determines a reactive force of a wire member by a sensor, used for the transmission of a driving signal between the robot apparatus and a joint (or end effector). The robot apparatus includes: a plurality of links which constitute a robot arm; rotational joints which connect each of the links to each other; a motor which drives each of the rotational joints; and a cable as a wire member, which is arranged along each link and transmits a driving signal at least to a driving source. A controlling apparatus drives and controls the motor which drives the rotational joints, based on a value of a reactive force, which a cable reactive force measuring unit outputs, which measures the reactive force to be applied to a joint portion when the cable is deformed.