Power Unit Control System for Oscillation Suppression
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Solution Overview
Problem
Existing power units for robot joints struggle to control driving force effectively due to the influence of springiness in power transmission elements and rotational friction, leading to oscillation phenomena, as they do not account for the springiness of these elements or the viscosity of the output shaft.
Innovation Solution
A control system that includes a force detecting unit, displacement motion detecting unit, basic command value determining unit, actuator control unit, and manipulated variable determining unit, which corrects the driving force applied to the element to be driven by accounting for inertial forces and the springiness of the power transmission element, thereby stabilizing the force application and suppressing oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power transmission element (such as a reduction gear) is used to transmit driving force from the actuator to the spring member, then the driving force can be transmitted effectively, but the springiness of the power transmission element causes oscillation phenomenon in the driving force applied to the element to be driven
Solution Approach 1:
The patent implements feedback control by using an observer to estimate the state variables (including the influence of springiness) of the power transmission element, and then correcting the actuator output based on these estimates. The control unit adjusts the actuator's driving force according to the estimated springiness influence, thereby suppressing oscillations and stabilizing the driving force applied to the element to be driven.
Solution Approach 2:
The patent changes the control parameters by introducing estimated values of springiness influence as additional control variables. The observer estimates the springiness parameters in real-time, and these estimated parameters are used to dynamically adjust the actuator control commands, transforming the system from open-loop to closed-loop control with respect to the springiness effects.
2Stability of the object's composition
If an observer is used to suppress backlash oscillation of the gear, then the oscillation can be suppressed, but the technique does not take into account the influences of rotational friction or viscosity of the output shaft, preventing the driving force from following the desired value
Solution Approach 1:
The patent extends the observer's functionality to simultaneously estimate multiple influence factors including springiness, rotational friction, and viscosity effects. Instead of addressing only backlash oscillation, the enhanced observer estimates all relevant disturbance factors, enabling the control system to compensate for multiple sources of error and achieve both oscillation suppression and accurate driving force control.
3Measurement precision
If friction compensation using an observer is implemented, then the friction influence can be compensated, but the springiness of the power transmission element is not taken into account, causing the driving force to develop oscillation phenomenon
Solution Approach 1:
The patent merges the friction compensation function with the springiness compensation function into a unified observer-based control system. The observer simultaneously estimates both friction forces and springiness influences, and the control unit combines both compensation actions in a single control command, thereby achieving both friction compensation and springiness oscillation suppression through an integrated approach.
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
The control system ensures high stability in controlling the driving force applied to the element, effectively suppressing oscillations and maintaining the force close to the desired value by compensating for the influences of elastic, frictional, and viscous forces.
Implementation Method 1
a spring member, which receives the driving force of the actuator through the intermediary of a power transmission element, converts the received driving force into an elastic force and imparts the elastic force to the element to be driven
Implementation Method 2
the power transmission element being configured to exhibit springiness between an input section thereof adjacent to the actuator and an output section thereof adjacent to the spring member
Data Source
AI summary
A control system of a power unit in accordance with the present invention corrects a basic command value of an electric motor 2, which has been determined such that the detection value of a driving force to be applied to a rotary member 5 is converged to a desired value, according to a manipulated variable determined by an observer 16. The electric motor 2 is controlled according to a desired control value after the correction. The observer 16 determines the manipulated variable such that the driving force based on the desired control value is brought close to the resultant force of a force indicated by the rotary member 5 and an inertial force.