Electric Vehicle PTO Control With Independent Direction and Speed
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Solution Overview
Problem
Electric vehicle power take-offs face challenges in providing rotational power in the desired direction and at the correct speed, especially at low vehicle speeds, which are not adequately addressed by existing systems.
Innovation Solution
A propulsion system incorporating a first and second electric machine, a transmission, a disconnect clutch, a power take-off, and controllers to manage the clutches, allowing independent control over power take-off direction and speed, enhancing the capability of electric machines to supply power to external devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a power take-off is integrated into an electric vehicle powertrain, then power can be supplied to external devices, but the power take-off cannot provide rotational power in the desired direction when the vehicle is traveling in forward or reverse gear
Solution Approach 1:
The powertrain is divided into two separate electric machines: a first electric machine coupled to the power take-off for dedicated PTO operation, and a second electric machine coupled to the transmission for vehicle propulsion. This segmentation allows independent control of PTO rotation direction from vehicle motion direction, resolving the contradiction between adaptability and ease of operation.
2Adaptability or versatility
If a power take-off is integrated into an electric vehicle powertrain, then power can be supplied to external devices, but the power take-off cannot rotate at a desirable speed when the vehicle is traveling at low speed
Solution Approach 1:
By separating the PTO function into a dedicated first electric machine independent of the vehicle transmission system, the PTO rotation speed can be controlled separately from vehicle speed. This allows the PTO to rotate at desirable speeds even when the vehicle is traveling at low speed, as the first electric machine can operate independently of vehicle motion conditions.
3Device complexity
If a single electric machine is used for both propulsion and power take-off, then device complexity is reduced, but the capability to independently control power take-off direction and speed is lost
Solution Approach 1:
The system uses two electric machines to provide independent control capability. The first electric machine is dedicated to the power take-off while the second handles vehicle propulsion, allowing independent control of PTO direction and speed. This segmentation accepts increased device complexity as a necessary trade-off to achieve the required adaptability and independent control.
Solution Approach 2:
Each electric machine is designed with multi-functionality considerations. The first electric machine can operate in motor mode to drive the PTO and in generator mode to be driven by the PTO for energy recovery. The second electric machine provides vehicle propulsion. This multi-functionality allows the system to maintain reasonable complexity while achieving versatile control capabilities.
Data Source
AI summary
Methods and systems for controlling a power take-off and engagement of an electric machine of an electric vehicle are described. In one example, a power take-off and engagement of a disconnect clutch are controlled in response to vehicle speed and tractive effort. A first electric machine is fixable coupled to a gear set of a transmission and the driveline disconnect clutch may selectively couple a second electric machine to the gear set.