Dynamometer Speed Control via Inertia Compensation Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current drive train test stands face challenges in simulating dynamic tests due to high inertia in chassis dynamometers, leading to unstable speed control and increased costs for high-performance dynamometers, and existing solutions either lack closed-loop control or require complex controller tuning.
Innovation Solution
The method involves calculating a compensation torque in the control unit based on the difference between the dynamometer's moment of inertia and the simulated vehicle wheel's moment of inertia, which is then added to the setpoint torque to stabilize speed control and improve dynamometer performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chassis dynamometer is used to test a drive train, then the vehicle can be tested on a stationary platform, but the high inertia of the rollers prevents dynamic tests with rapid changes in speed and torque
Solution Approach 1:
The patent replaces the traditional mechanical chassis dynamometer system with high-inertia rollers with a drive train test stand using electrically controlled dynamometers. The mechanical system is substituted with an electrically controlled system where electric motors/dynamometers directly couple to the drive train components, enabling rapid torque and speed changes through electrical control rather than mechanical inertia.
Solution Approach 2:
The patent changes the fundamental parameter of moment of inertia by replacing heavy mechanical rollers with lightweight electrically controlled dynamometers. This parameter change allows the system to achieve high dynamic responsiveness while maintaining test reproducibility through precise electronic control of torque and speed parameters.
2Reliability
If the moment of inertia of the dynamometer is made close to that of the true wheel for realistic tests, then the simulation becomes more accurate, but high-performance electric synchronous machines are required which increase cost and reduce reliability
Solution Approach 1:
The patent introduces a computational intermediary - a simulation model running on a control unit - that mediates between the dynamometer and the drive train. The simulation model calculates the virtual wheel's moment of inertia and uses this information to generate appropriate torque commands, allowing the physical dynamometer to have different inertia characteristics while still achieving realistic simulation through software compensation.
Solution Approach 2:
The patent changes the approach from matching physical parameters (moment of inertia) to using computational parameters. The simulation model uses the virtual wheel's moment of inertia for realistic simulation, while the physical dynamometer operates with its own characteristics, decoupling the requirement for expensive high-performance machines.
3Device complexity
If an open-loop torque control is used with the dynamometer, then the control system is simpler, but control errors and deviations cannot be compensated
Solution Approach 1:
The patent implements feedback control by continuously measuring the actual speed of the side shaft and comparing it with the target speed from the simulation model. The control unit uses this feedback information to calculate and adjust the torque commands to the dynamometer, compensating for deviations and ensuring accurate tracking of the simulated driving conditions.
Data Source
AI summary
The present teaching includes a speed control of a side shaft of a drive train connected to a dynamometer on a drive train test stand in which a torque (MFxi) caused by the longitudinal force (FXi) calculated in a simulation model is additionally transferred to the control unit, and from this a compensation torque (MKi) is calculated in the control unit as a function of the longitudinal force (FXi) caused by the torque (MFxi) and a deviation (AJi) between a moment of inertia (JBi) of the dynamometer and a moment of inertia (JRi) of the simulated vehicle wheel, the control unit calculates a torque (MREi,) from the setpoint speed (nBi,set) with a speed controller and a torque (MBi,soll) to be set with the dynamometer is calculated as the sum of the compensation torque (MKi) and the torque (MREi) calculated by the speed controller and set by the dynamometer.