Tandem Dynamometer Mechanical Characteristic Estimation
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Solution Overview
Problem
Existing test systems with tandem dynamometers face challenges in accurately measuring mechanical characteristics due to the influence of control circuit characteristics, which are reflected in the mechanical characteristics transfer function, making it difficult to design effective resonance suppression circuits.
Innovation Solution
A method and device that estimate mechanical characteristics by measuring responses to excitation signals applied to each electric motor under controlled conditions, allowing for the separation of true mechanical characteristics from control circuit characteristics, using a shaft torque sensor and speed detectors in conjunction with a control device to generate and analyze input and output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement method is used to measure mechanical characteristics transfer function, then measurement can be performed, but control circuit characteristics are reflected in the measurement results, making it impossible to obtain true mechanical properties
Solution Approach 1:
The patent segments the measurement process into two distinct phases: first measuring the control circuit characteristics separately by applying excitation signals while the system operates under normal control, then measuring the combined system characteristics. This allows the control circuit characteristics to be isolated and subtracted from the total measurement, leaving only the true mechanical characteristics. The segmentation enables independent characterization of control circuit behavior from mechanical system behavior.
Solution Approach 2:
The patent extracts the control circuit characteristics from the overall system response by performing a separate measurement of the control circuit's transfer function. This extracted control circuit characteristic is then removed from the combined measurement results through mathematical operations (division in the frequency domain), effectively taking out the unwanted control circuit influence and leaving only the pure mechanical characteristics.
2Force
If tandem dynamometer configuration is used to generate large drive torque, then torque capacity is improved, but resonance suppression becomes difficult due to shaft twist
Solution Approach 1:
The patent implements feedback control by continuously measuring the actual mechanical characteristics (moment of inertia, spring stiffness, damping coefficients) using the extracted pure mechanical transfer functions, and using these measured values to update the resonance suppression control parameters. This closed-loop feedback ensures that the resonance suppression circuit is always tuned to the actual mechanical conditions of the tandem dynamometer system, compensating for variations and maintaining stability.
Solution Approach 2:
The patent changes the parameters of the resonance suppression control based on the measured mechanical characteristics. By dynamically adjusting control parameters (such as feedback gains, filter frequencies, and damping coefficients) according to the actual moment of inertia and spring stiffness values obtained from measurement, the system optimizes resonance suppression performance for the specific tandem dynamometer configuration.
Data Source
AI summary
A drive train bench system has two dynamometers that are connected in series to a specimen. The mechanical characteristics estimation method has: a first measurement step for measuring a response to a first excitation torque input signal when the first excitation torque input signal overlaps a first torque current command signal while a measurement control circuit controls the two dynamometers; a second measurement step for measuring a response to a second excitation torque input signal when the second excitation torque input signal overlaps a second torque current command signal while the measurement control circuit controls the two dynamometers; and a mechanical characteristics transfer function estimation step for using the results from the first and second measurement steps to estimate a mechanical characteristics transfer function.