Movement Simulator Torque Compensation for Joint Interaction Stability
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Solution Overview
Problem
Conventional movement simulators face challenges in accurately compensating for Coriolis, centrifugal, and gravitational torques due to their monovariable control laws, which fail to explicitly account for interactions between joints, leading to instability, especially at high rotational speeds.
Innovation Solution
A multivariable control law is implemented, combining a monovariable corrector block with a non-linear compensation law that estimates and compensates for disturbing torques by using a dynamic model and adaptive parameter estimation, injecting the estimation into the command signal to improve torque control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If monovariable control laws are used in movement simulators, then the control structure is simple and easier to implement, but the speed stability and position accuracy deteriorate at high rotational speeds due to unaccounted joint interactions
Solution Approach 1:
The control system is segmented into two distinct parts: a monovariable corrector block that handles basic control functions with simple structure, and a separate multivariable compensation block that specifically addresses joint interaction effects. This segmentation allows each block to specialize in its function while maintaining overall system manageability.
Solution Approach 2:
A multivariable compensation block is introduced as an intermediary element between the monovariable corrector and the plant. This compensation block calculates and injects corrective torques that account for Coriolis, centrifugal, and gravitational effects, thereby mediating the interaction between joints and improving speed stability without requiring complete redesign of the entire control system.
2Ease of operation
If monovariable control laws are used, then the control implementation is straightforward, but position accuracy deteriorates due to indirect and insufficient compensation of disturbing torques
Solution Approach 1:
The multivariable compensation block performs preliminary calculations of disturbing torques based on measured joint positions and speeds before these disturbances affect the system performance. By computing compensation torques in advance and injecting them into the control signal, the system proactively counteracts Coriolis, centrifugal, and gravitational effects, thereby maintaining position accuracy.
Solution Approach 2:
The system continuously measures actual joint positions and speeds, feeds this information back to the multivariable compensation block, which then recalculates and adjusts the compensation torques in real-time. This feedback mechanism ensures that the compensation remains accurate despite changes in system state, thereby maintaining high position accuracy throughout operation.
3Device complexity
If conventional corrector-based control is used, then the system is easier to design and implement, but the compensation of Coriolis, centrifugal and gravitational torques is insufficient at high speeds
Solution Approach 1:
The compensation block dynamically adjusts its compensation torques based on real-time measurements of joint positions and speeds. The compensation calculations adapt to changing operating conditions, particularly at high rotational speeds where Coriolis, centrifugal, and gravitational effects become significant. This dynamic adaptation allows the system to maintain performance across a wide range of operating conditions without requiring complete redesign.
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
This approach significantly alleviates the impact of disturbing torques, enhancing speed stability and position accuracy in movement simulators by explicitly accounting for joint interactions, thereby improving performance.
Implementation Method 1
compensating for Coriolis, centrifugal and gravitational torques
Implementation Method 2
compensating for Coriolis, centrifugal and gravitational torques
Implementation Method 3
compensating for Coriolis, centrifugal and gravitational torques
Data Source
AI summary
Disclosed is a method for compensating for disturbing couples for a movement simulator, the simulator including, for each axis, a monovariable correcting unit that receives a signal giving the difference between the setpoint θrj and the measurement θj for the corresponding axis and producing the control signal Uj. The disruptive couples are Coriolis, centrifugal and gravitational couples and furthermore a compensating law calculates a formula (a) estimating the disruptive couples, calculated on the basis of an error εj(t) that is the control signal Uj filtered by a filter H(q−1), and the simulator is modelled with a dynamic model expressing the couples in an affine way with respect to a set of base parameters χ according to a matrix relationship of the type: formula (b), and a subset j of base parameters, the estimation of the couples being formula (c), and, online, the αj are calculated via an iterative equation.