Configuration-Dependent Vibration Control With Consistent Feedforward
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Solution Overview
Problem
Current vibration suppression methods for systems with configuration-dependent dynamic parameters, such as collaborative robots, face challenges in handling time-varying dynamics and discrete time implementation, leading to inconsistent feedforward inputs and increased vibrations.
Innovation Solution
A method is introduced that generates a modified input signal for a physical system or robot by convolving part of an input buffer with an impulse train, where the impulse train is based on the dynamic properties of the system, using a new discrete time buffer implementation that ensures a constant unity sum of applied impulses, and employing numerical differentiation to obtain consistent feedforward derivatives without phase lag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If light weight structures are used to reduce mass and inertia, then the risk of human or material damage in impact situations is reduced, but the reduced mass and inertia result in reduced stiffness and reduced damping, thereby increasing system vibrational behavior
Solution Approach 1:
The patent applies preliminary action by predicting the system's vibrational behavior beforehand and compensating for it through pre-calculated feedforward control inputs. The method computes the system's dynamic response to desired trajectories and anticipates vibrations before they occur, allowing corrective actions to be built into the control signal in advance. This resolves the contradiction by maintaining light weight structures while preemptively counteracting their inherent vibrational tendencies through predictive control.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting control parameters based on the system's configuration-dependent dynamic parameters. The method calculates time-varying feedforward control signals that adapt to changing system parameters such as mass, inertia, and stiffness as the system moves through different configurations. This allows the lightweight system to maintain optimal performance across varying operational states while compensating for reduced damping and stiffness through adaptive parameter adjustment.
2Device complexity
If open loop vibration reduction method is used, then a simpler control structure is achieved and additional sensors are avoided, but the system must predict the behavior of the system which increases computational complexity
Solution Approach 1:
The patent applies copying by creating a computational model (copy) of the system's dynamic behavior that mirrors the physical system's characteristics. This digital twin or virtual model is used to predict vibrations and compute feedforward control signals without requiring physical sensors on the actual system. The computational model captures the essential dynamics including configuration-dependent parameters, allowing accurate prediction and compensation of vibrations while keeping the physical control structure simple and sensor-less.
3Measurement precision
If configuration-dependent dynamic parameters are used in discrete time implementation, then the system model accuracy is improved, but inconsistent feedforward inputs are generated leading to increased vibrations
Solution Approach 1:
The patent applies dynamics by explicitly accounting for the time-varying nature of configuration-dependent dynamic parameters in the discrete-time control implementation. The method computes feedforward control signals that adapt to changing system parameters at each time step, using the current configuration to determine the appropriate dynamic parameters. This dynamic adaptation ensures consistency between the system model and actual behavior, preventing vibrations caused by parameter mismatches while maintaining high model accuracy.
Solution Approach 2:
The patent employs feedback by using the system's actual configuration and state information to adjust the feedforward control signals. Although primarily an open-loop method, it incorporates feedback elements by continuously updating the configuration-dependent dynamic parameters based on measured or estimated system state. This ensures that the feedforward inputs remain consistent with the actual system behavior, eliminating vibrations caused by parameter inconsistencies while maintaining the simplicity of open-loop control structure.
Data Source
AI summary
A method is provided for vibration suppression, which is useful in systems with configuration dependent dynamic parameters. The method is a general and practical solution for obtaining a set of inputs to a dynamic system, which will result in reduced vibrational behavior. A novel discrete time buffer implementation is employed, which yields reduced vibration due to a constant unity sum of applied impulses. The method includes shaping a position input with a continuously updated filter and using numerical differentiation to obtain consistent feedforward derivatives without phase shift.