Powertrain Lash Closure Rate Management
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Solution Overview
Problem
Existing driveline lash management systems face challenges in accurately determining lash state transitions, especially at low speeds, due to poor resolution of rotary speed sensors, which can lead to undesirable noise, vibration, and harshness during torque reversal events in powertrain systems.
Innovation Solution
An open-loop lash state transition management methodology using a controller with a capped output torque request table and a lash closure rate estimate table, integrated with a driveline proportional-integral control block, allows for accurate output speed calculation and control of the powertrain system without relying on wheel speed sensors, particularly effective in systems with low-inertia electric motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wheel speed sensors are used for lash management, then control feedback is available, but system complexity increases and robustness decreases at low speeds
Solution Approach 1:
The patent extracts the speed sensing function from the physical domain and relocates it to the computational domain. By removing the dependency on wheel speed sensors and implementing speed estimation through a driveline model that processes torque requests and system parameters, the patent eliminates the hardware complexity while maintaining control capability.
Solution Approach 2:
The driveline system uses its own operational parameters (torque requests, gear ratios, inertial properties) to self-determine its state. The controller leverages information already available in the control system to estimate speed and detect lash transitions, making the system self-sufficient without external sensors.
2Use of energy by moving object
If low-inertia electric motors are used, then powertrain efficiency is improved, but lash transition control becomes more difficult due to reduced momentum
Solution Approach 1:
The patent applies preliminary action by using the driveline model to predict and prepare for lash state transitions before they occur. The controller continuously estimates the driveline state and anticipates lash transitions, allowing it to proactively adjust control commands to manage the transition smoothly, compensating for the low inertia of electric motors.
Solution Approach 2:
The patent implements a dynamic control approach where the controller continuously updates the driveline model with current torque requests and system parameters. This dynamic estimation adapts to changing operating conditions and compensates for the reduced momentum of low-inertia motors, maintaining control stability throughout the operating range.
Data Source
AI summary
A powertrain system includes a transmission, torque generating device, load coupled to a drive axle, a final drive unit in meshed gear engagement with the output shaft and the drive axle, and a controller. A requested output torque is processed using an open-loop lash state model populated with a capped output torque request table and a lash closure rate estimate table respectively providing a capped torque value and an estimated lash closure rate. Output speed is determined using a plant model, the capped torque value, and the estimated lash closure rate. The powertrain is controlled during the transition using the output speed. A lash angle may be calculated from the closure rate using an integrator logic block. A calibrated lash offset profile may be determined using the lash angle, and a reference speed may be generated using the lash offset profile.