Hybrid Transmission Shift Control via Torque Forecasting
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Solution Overview
Problem
Automatic transmissions in hybrid vehicles experience 'powertrain hunting' due to rapid successive gear shifts caused by inadequate consideration of actual vehicle load and dynamic operating conditions, leading to reduced driver satisfaction.
Innovation Solution
A powertrain controller that forecasts sustainable torque based on driver torque demand, vehicle speed, and energy available from the traction battery, permitting upshifts only when the forecasted available torque exceeds the demand and inhibiting upshifts when torque demand exceeds sustainable torque, thereby reducing unnecessary gear shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a predetermined shift schedule map is used to determine transmission gear shifts, then the transmission can operate with simple control logic, but the system cannot dynamically adapt to actual vehicle load conditions, causing powertrain hunting and reduced driver satisfaction
Solution Approach 1:
The controller forecasts future powertrain torque availability before making shift decisions, preparing for potential torque deficits in advance. This preliminary assessment prevents reactive shifting that causes powertrain hunting, allowing the system to maintain simplicity while improving adaptability to dynamic load conditions.
Solution Approach 2:
The system continuously monitors actual vehicle load conditions and battery energy availability, using this feedback to dynamically adjust shift timing. This closed-loop approach enables the transmission to adapt to real-time operating conditions without requiring complex mechanical modifications, resolving the contradiction between simplicity and adaptability.
2Ease of operation
If transmission upshifts are permitted based on traditional shift schedules, then gear shifts occur at predetermined points, but successive upshifts and downshifts occur rapidly under varying load conditions, reducing driver satisfaction
Solution Approach 1:
The controller performs preliminary torque forecasting to anticipate future power availability before executing upshifts. By assessing whether sufficient torque will be available in the upcoming time window, the system prevents premature upshifts that would later require corrective downshifts, thereby ensuring stable gear ratio selection and smooth power delivery.
Solution Approach 2:
The system applies preliminary anti-action by inhibiting upshifts when forecasted torque availability indicates potential deficits. This preventive measure counteracts the tendency to shift too early, avoiding the harmful cycle of successive upshifts and downshifts, thus maintaining reliable and stable transmission operation.
Data Source
AI summary
A vehicle is provided with a powertrain including a battery-powered electric motor, an internal combustion engine, a transmission, and a powertrain controller. The controller is programmed to permit an upshift of a transmission gear ratio while a powertrain torque demand is less than a forecasted available powertrain torque sustainable over a predetermined upcoming duration of time. The controller is also programmed to inhibit an upshift while the torque demand exceeds the forecasted available powertrain torque to reduce successive gear shifts. The controller may be further programmed to, in response to battery a state of charge being less than a threshold, reduce the forecasted available powertrain torque by an amount sufficient to provide a recharge to a battery. The controller may be further still programmed to reduce the forecasted available powertrain torque by an amount sufficient to restart the engine while the powertrain is operating in an engine-off traction mode.