Legged Robot Inertial Sensor Gain Control for Foot-Impact Noise
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Solution Overview
Problem
Legged robots experience spurious vibrations when their feet contact surfaces, leading to unstable control systems due to amplified noise in inertial sensors, which can cause unnecessary corrections and instability.
Innovation Solution
A control system adjusts the gain value of amplifiers in response to foot contact, reducing the gain during vibrations and gradually increasing it back to nominal levels over time, based on vibration characteristics and robot dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gain value of the amplifier is increased to improve control responsiveness, then the control system becomes more responsive, but sensor noise is amplified causing instability
Solution Approach 1:
The patent applies dynamics by making the amplifier gain value time-varying rather than constant. The gain is adjusted dynamically based on the detected vibration state: during vibration periods, the gain is reduced to prevent noise amplification, while during stable periods, the gain is increased for better responsiveness. This dynamic adaptation resolves the contradiction between responsiveness and stability.
Solution Approach 2:
The patent uses feedback by continuously monitoring sensor measurements to detect vibration states and using this information to adjust the amplifier gain value. The control system receives feedback from the inertial sensor about foot contact and vibration, then modulates the gain accordingly, creating a closed-loop system that balances responsiveness and stability.
2Reliability
If the gain value is reduced to minimize vibration impact, then control stability improves, but control responsiveness deteriorates
Solution Approach 1:
The patent applies periodic action by alternating between different gain values based on the periodic nature of vibration during foot contact. The gain is reduced during the periodic vibration phase when foot contacts the surface, then restored to nominal levels when vibration subsides. This periodic modulation of gain maintains stability during critical moments while preserving responsiveness during stable periods.
3Speed
If nominal gain value is used continuously, then control responsiveness is maintained, but spurious measurements cause unnecessary corrections
Solution Approach 1:
The patent applies preliminary action by detecting foot contact before the full vibration effect occurs and proactively reducing the gain value in anticipation of spurious measurements. The control system monitors for foot contact events and preemptively adjusts the gain to prevent the amplification of upcoming vibration noise, rather than reacting after the noise has already corrupted control signals.
Data Source
AI summary
An example implementation involves receiving measurements from an inertial sensor coupled to the robot and detecting an occurrence of a foot of the legged robot making contact with a surface. The implementation also involves reducing a gain value of an amplifier from a nominal value to a reduced value upon detecting the occurrence. The amplifier receives the measurements from the inertial sensor and provides a modulated output based on the gain value. The implementation further involves increasing the gain value from the reduced value to the nominal value over a predetermined duration of time after detecting the occurrence. The gain value is increased according to a profile indicative of a manner in which to increase the gain value of the predetermined duration of time. The implementation also involves controlling at least one actuator of the legged robot based on the modulated output during the predetermined duration of time.