Master-Slave Force-Projecting Control for Stable Teleoperation
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Solution Overview
Problem
Conventional bilateral control systems face issues such as unstable behavior due to contact with hard environments, limited stability, inadequate consideration of human sensing abilities, impaired operability at singularities, and low backdrivability, which affect the ability of operators to feel dynamic behavior of slave robots and environments.
Innovation Solution
A master-slave system employing force-projecting bilateral control, where a single-axis force sensor measures the slave effective driving force, allowing the operator to feel external dynamics without internal slave actuator dynamics, and enabling robust and accurate master robot operation without requiring backdrivability in the slave robot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If force-reflecting bilateral control is used to allow operators to feel external dynamics, then operator feedback is improved, but internal slave actuator dynamics interfere with the feedback signal
Solution Approach 1:
The patent extracts only the necessary force information (slave effective driving force) from the slave system while leaving out the harmful internal dynamics. By measuring only the force actually acting on the terminal output axis and transmitting only this purified signal to the master side, the system removes the interference of internal actuator dynamics from the operator feedback loop.
Solution Approach 2:
The patent introduces an intermediary measurement device (force sensor) at the terminal output axis of the slave actuator. This intermediary captures the pure effective driving force and transmits it to the master side, acting as a buffer that separates the operator feedback from the harmful internal dynamics of the slave actuator.
2Strength
If the slave robot is made mechanically robust with high reduction ratio, then it can withstand human power, but backdrivability decreases and operator cannot feel slave dynamics
Solution Approach 1:
The patent replaces the mechanical backdrivability mechanism with an electronic sensing and feedback system. Instead of relying on the mechanical structure to provide backdrivability through friction and gear backlash, the system uses force sensors to measure the effective driving force and electronically transmits this information to the master side, allowing robust mechanical design without sacrificing operator awareness of slave dynamics.
3Measurement precision
If working force sensor is mounted at slave working end to measure slave working force, then force measurement accuracy is improved, but system complexity and instability risk increase
Solution Approach 1:
Instead of measuring the slave working force directly at the working end as conventionally done, the patent inverts the approach by measuring the slave effective driving force at the actuator output axis. This inverted measurement location provides equivalent or superior information for control purposes while avoiding the complexity and instability risks associated with mounting sensors at the slave working end.
4Ease of operation
If master robot is designed with low inertia and friction for high backdrivability, then operability is improved, but master robot becomes fragile and less accurate
Solution Approach 1:
The patent replaces the need for mechanically optimized low-inertia master robot design with an electronic control system that uses force sensors and computational algorithms. This substitution allows the master robot to have higher inertia and friction for robustness while maintaining operability through electronic compensation and feedback control.
Data Source
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AI summary
A master-slave system (1) according to the present invention includes a slave actuator (As1 to As3) for generating a slave driving force (τs) to control a slave robot in terms of driving force, an effective driving force sensor (Fs1 to Fs3) for measuring a slave effective driving force (τsa) actually acting on a terminal output axis of the slave actuator (As1 to As3), and a slave target effective driving force calculating device (3) for calculating a slave target effective driving force (τsad) which is a target value for the slave effective driving force (τsa), on the basis of a master operating force (fm) applied to the master robot by an operator (U). The slave actuator (As1 to As3) generates the slave driving force (τs) on the basis of the slave target effective driving force (τsad) and the slave effective driving force (τsa).