Powertrain Test Stand Torque Control via Virtual Tire Model
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Solution Overview
Problem
Existing drive train test bench systems face challenges in effectively damping resonance frequencies, leading to vibrations that can impact test results or cause damage, due to delayed and noisy measurement values, and existing methods are either inefficient or unstable at higher frequencies.
Innovation Solution
A method using a tire model to control the torque of the input machine, where a virtual tire is used to determine the command variable for damping, avoiding the need for precise measurement of multiple speeds and reducing the influence of dynamic variables, with a static relationship between slip and torque setpoint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If softer, more strongly damped connecting shafts are used to lower and dampen resonance frequencies, then the resonance frequencies are dampened more strongly, but the low-pass effect adversely affects operation and power is converted to heat due to friction
Solution Approach 1:
The patent replaces the mechanical damping approach (soft connecting shafts with friction) with an electrical control system. The control device applies electromagnetic torque to the input machine to counteract resonance vibrations, eliminating the need for friction-based mechanical damping and the associated energy loss to heat.
Solution Approach 2:
The patent introduces a control device as an intermediary between the measurement systems and the input machine. This control device processes speed measurements and applies corrective torque to dampen resonances, serving as a mediator that eliminates the need for direct mechanical damping through soft shafts.
2Object-affected harmful factors
If additional torque corresponding to shaft damping is applied to the driven machine using differential angular velocity, then resonance frequencies are dampened, but measurement noise and delay make the powertrain test stand more unstable
Solution Approach 1:
The patent implements a feedback control system that continuously measures the speeds of the input and output machines, calculates the differential angular velocity, and applies corrective torque to dampen resonances. This closed-loop feedback approach maintains system stability by continuously adjusting the damping torque based on actual system state.
Solution Approach 2:
The patent employs dynamic control by adjusting the damping torque in real-time based on the measured differential angular velocity. The control device modifies the torque applied to the input machine dynamically to counteract resonance vibrations, rather than using fixed mechanical damping.
3Measurement precision
If measured shaft torque is differentiated to estimate differential angular velocity, then damping accuracy is improved, but measurement noise is significantly amplified
Solution Approach 1:
The patent replaces the mathematical differentiation operation (which amplifies noise) with direct measurement and processing of speed signals. The control device uses measured speeds of the input and output machines to calculate differential angular velocity, avoiding the noise amplification inherent in differentiation of torque signals.
Solution Approach 2:
The patent introduces speed measurements as an intermediary variable to estimate differential angular velocity. Instead of differentiating torque (which amplifies noise), the system uses speed measurements as a mediator to achieve accurate differential velocity estimation without noise amplification.
4Object-affected harmful factors
If low-pass filtering is applied to differentiated torque to reduce noise, then measurement noise is reduced, but the method becomes unstable at higher resonance frequencies
Solution Approach 1:
The patent implements feedback control using directly measured speed signals rather than filtered and differentiated torque signals. This approach maintains stability across all frequency ranges by using clean, direct measurements and real-time feedback to adjust damping torque, avoiding the frequency-dependent stability issues of filtered differentiation methods.
Solution Approach 2:
The patent replaces the signal processing chain of differentiation followed by low-pass filtering with direct speed measurement and processing. This substitution eliminates the fundamental conflict between noise reduction and high-frequency stability by using a different measurement approach from the start.
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 effectively dampens low-frequency vibrations, is insensitive to measurement noise, and maintains stability during transient tests, improving the accuracy and safety of drive train testing by utilizing the damping effect of the tire model at the input machine.
Implementation Method 1
measures to dampen these resonance frequencies on the test bench are necessary
Implementation Method 2
a not inconsiderable amount of power can be converted in the shaft due to friction
Data Source
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AI summary
Disclosed are a method and a control device for controlling a powertrain test stand comprising a driving machine and a driven machine. According to the invention, a torque supplied by the driving machine is controlled, a reference variable (Mx) for controlling the torque of the driving machine in order to dampen vibrations between the driving machine and the driven machine being modified depending on a current speed (nist) of the driving machine in relation to a predefined value (Mist), the reference variable (Mx) being determined from a model of a virtual tire.