Hinged Comanipulator Segment Control via H-Infinity Torque Synthesis
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Solution Overview
Problem
Existing control methods for comanipulator arms, such as master arms and exoskeletons, face challenges in compensating for the inertia of actuators, which affects user experience due to the amplification of motor inertia by reducers, leading to irregular acceleration signals and reduced performance in compensating for inertia forces.
Innovation Solution
A method that estimates the inertia and minimal joint viscous friction of the segment, measures movement speed and internal deformation, and synthesizes a type control law to generate a control torque, meeting performance objectives that erase the effects of flexibility in the actuation, using H∞ control law and constraints on supply current, pole positions, and passivity to ensure a transparent user experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a reducer with high amplification ratio is used to amplify motor torque, then the torque generation capability is improved, but the motor inertia is multiplied by the square of the amplification ratio, making it perceptible to the user and reducing transparency
Solution Approach 1:
The invention changes the control parameters by synthesizing an H∞ control law that explicitly accounts for the amplified inertia. The control law transforms the system dynamics to compensate for the inertia multiplication effect, allowing the use of high amplification ratio reducers while maintaining transparency. The control torque is calculated to counteract the perceived inertia forces, effectively decoupling the torque amplification benefit from the inertia penalty.
2Measurement precision
If acceleration is estimated from position signal by double derivation, then acceleration signal is obtained, but the signal becomes irregular and requires powerful filtering that reduces control performance
Solution Approach 1:
The invention replaces the mechanical differentiation process (double derivation of position) with a model-based approach. Instead of numerically differentiating position signals, the system uses a dynamic model that directly computes acceleration from measured variables, avoiding the signal irregularities and filtering requirements associated with numerical differentiation.
Solution Approach 2:
The invention introduces an intermediary computational model that acts as a mediator between position measurement and acceleration estimation. This model-based intermediary processes the position signal through a controlled mathematical transformation that preserves signal quality while providing accurate acceleration estimates for control purposes.
3Reliability
If H∞ control law is used to optimize vibration compensation, then vibration compensation performance is improved, but the complexity of control synthesis increases
Solution Approach 1:
The invention changes the control synthesis parameters by formulating the H∞ control law with specific performance objectives related to the transfer function between segment acceleration and external force. By parameterizing the control law synthesis around these specific objectives, the complexity is managed while achieving optimized vibration compensation.
Data Source
AI summary
The invention relates to a method for controlling an actuator (1) of a hinged segment (5) comprising the steps of: estimating an inertia J of the segment and a minimum viscous hinge friction f; estimating or measuring a traveling speed Ẋ of the segment and an internal deformation ΔX of the actuator; synthesizing a control law H ∞ generating a control current (or torque) from said estimates or measurements and meeting a performance objective pertaining to a transfer function (I) between an acceleration Ẍ of the segment and an external force F to which the segment is subjected: (II) with (III), ε being a mathematical artifact and s being the Laplace variable; and controlling the actuation of the hinged segment according to the control law thus synthesized.