Vehicle Drive Force Control Using Virtual Manual Transmission Torque
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Solution Overview
Problem
Existing drive force control systems for vehicles with electric motors struggle to accurately imitate the shift feel of manual transmissions due to differences in powertrain structures between electric vehicles and those with internal combustion engines, leading to inconsistent drive force changes.
Innovation Solution
A drive force control system that includes a controller with a drive torque simulator and an actual torque calculator, which compute virtual and target torques based on inertia moment, elastic coefficient, and attenuation coefficient of the powertrain, simulating the behavior of a model vehicle with a manual transmission to mimic the driving experience of a conventional vehicle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If motor torque is controlled based on engine torque characteristics with time constant and dead time, then the shift feel of manual transmission can be imitated, but the drive force change is not accurate due to structural differences in power transmission
Solution Approach 1:
The patent creates a virtual model vehicle with engine and transmission characteristics, copying the torque transmission behavior of conventional vehicles. The drive torque simulator computes virtual drive torque based on engine torque and transmission characteristics, rather than directly controlling motor torque based on engine characteristics. This copying approach allows accurate reproduction of manual transmission shift feel while accounting for structural differences.
Solution Approach 2:
The patent introduces a drive torque simulator as an intermediary between the motor controller and the driver's perception. Instead of directly controlling motor torque, the system simulates what the drive torque would be in a model vehicle with manual transmission, then uses this simulated torque as the control target. This intermediary layer resolves the contradiction by decoupling the control objective from the direct motor torque control.
2Ease of operation
If motor torque is temporarily decreased to create virtual shift shock, then the driver can feel the shift sensation, but the drive force change does not match manual transmission behavior
Solution Approach 1:
The patent dynamically adjusts motor torque control based on simulated drive torque from the drive torque simulator. Rather than using fixed torque reduction patterns, the system continuously computes the virtual drive torque considering current vehicle state, transmission gear stage, and accelerator operation. This dynamic approach ensures both shift sensation and drive force consistency match manual transmission behavior under varying conditions.
Solution Approach 2:
The system uses feedback from the drive torque simulator to continuously adjust motor torque control. The simulator computes virtual drive torque based on engine torque and transmission characteristics, and this computed torque feeds back to the motor controller as the control target. This closed-loop feedback ensures that torque changes produce both shift sensation and consistent drive force behavior matching manual transmission.
3Ease of operation
If pseudo shift change is performed by torque variation control, then virtual shift shock can be generated, but the drive force profile differs from actual manual transmission
Solution Approach 1:
The patent changes the control parameter from direct motor torque control to simulated drive torque control. The drive torque simulator computes virtual drive torque using engine torque, transmission gear stage, and vehicle speed as inputs. By changing the control parameter to match what the driver perceives (drive torque at wheels) rather than motor torque, the system achieves both virtual shift shock and accurate drive force profile matching manual transmission.
Data Source
AI summary
A drive force control system for a vehicle configured to accurately imitate a change in a drive force in a model vehicle. A drive torque simulator computes a virtual drive torque supposed to be delivered to drive wheels of the model vehicle in response to a manual operation to manipulate the vehicle, based on torque changing factors of a powertrain of the model vehicle. An actual torque calculator computes a target torque of a motor that is practically delivered to the drive wheels in the vehicle based on the virtual drive torque computed by the drive torque simulator, taking account of torque changing factors of the powertrain of the vehicle.