Drivetrain Vibration Damping via Shaft Torque Feedback
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Solution Overview
Problem
Existing methods for damping vibrations in drivetrain test stands are either ineffective in transient tests, require knowledge of device or test stand parameters, or are unstable due to measurement noise, especially when dealing with resonance frequencies.
Innovation Solution
The method involves directly combining the measured shaft torque with the target value of the drive or load torque without differentiation, using a delay line and a frequency-dependent transfer function to achieve optimal damping, and adjusting the damping effect with a weighting factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a softer, more effectively damped coupling shaft is used to reduce resonance frequencies, then resonance frequencies are reduced and damped, but power is consumed by friction (heating and sometimes even destroying the shaft)
Solution Approach 1:
The patent replaces the mechanical damping approach (softer shaft with friction) with an active control system using sensors and actuators. The control unit calculates compensating torques based on measured shaft torque and applies them via actuators, eliminating the need for friction-based mechanical damping while achieving the same resonance suppression effect.
2Reliability
If the measured shaft torque is differentiated to estimate angular speed difference for active damping, then active damping can be achieved, but measurement noise is strongly amplified
Solution Approach 1:
The patent uses feedback control where the measured shaft torque is directly fed back to the control unit, which calculates the angular speed difference and determines compensating torques. This closed-loop feedback mechanism achieves active damping without differentiating the measured torque signal, thereby avoiding noise amplification while maintaining damping effectiveness.
3Measurement precision
If a low-pass filter is applied to the differentiated torque to reduce noise, then measurement noise is reduced, but the method becomes unstable at higher resonance frequencies
Solution Approach 1:
The patent substitutes the problematic signal processing chain (differentiation followed by low-pass filtering) with a direct feedback approach using measured shaft torque. This replacement eliminates the need for filtering while maintaining control stability across all resonance frequencies, including high frequencies.
4Reliability
If measured data are stored over a working cycle for predicting future target values, then resonance frequencies can be damped in steady-state, but the method does not work in transient tests and requires significant storage effort
Solution Approach 1:
The patent implements preliminary action by using real-time measured shaft torque to immediately calculate and apply compensating torques through the load machine. This approach provides immediate damping effect during both transient and steady-state operations without requiring historical data storage or prediction algorithms, eliminating the complexity associated with data storage while maintaining effective resonance suppression.
Data Source
AI summary
The invention relates to a method for damping vibrations while checking a drivetrain which has at least one shaft and to a device for carrying out the method. The shaft is connected to at least one drive or load machine for adjustment of a drive or load torque, a target value of the drive or load torque being specified for the machine. A shaft torque which is dependent on the relative rotation between two points on the shaft is measured, and the measured shaft torque as such is applied to the target value of the drive or load torque.