Electric Work Vehicle Mode Control for Speed and Blade Load Balance
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Solution Overview
Problem
Existing electric work vehicles, such as mowers, limit vehicle speed and work device rotation speed based on blade rotation speed, restricting the driver's ability to freely select speeds according to work type and area.
Innovation Solution
An electric work vehicle with a control unit that allows drivers to select from multiple work modes defining the relationship between vehicle speed and work device rotation speed, enabling independent adjustment of both speeds based on work details and area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vehicle speed and work device rotation speed are limited based on blade rotation speed, then the reliability of the work device is improved, but the ease of operation deteriorates because the driver cannot freely select speeds according to work type and area
Solution Approach 1:
The patent applies dynamics by making the control parameters (vehicle speed limit and work device rotation speed limit) adjustable rather than fixed. The mode selector allows dynamic switching between multiple work modes, each with different speed limit settings. This enables the system to adapt to different work conditions while maintaining reliability through controlled limits and providing operational flexibility through user-selectable modes.
Solution Approach 2:
The patent implements parameter changes by varying the speed limit parameters across different work modes. The control unit stores multiple sets of parameter values (vehicle speed limits and work device rotation speed limits) corresponding to different work modes. By changing these parameters based on the selected mode, the system resolves the contradiction between maintaining safe operational limits and allowing flexible speed selection for different work scenarios.
2Adaptability or versatility
If multiple work modes with different speed limits are provided, then the adaptability to different work conditions is improved, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent applies universality by designing a multi-functional control unit that handles both vehicle speed control and work device rotation speed control. The same control unit stores multiple work modes and manages both speed parameters, eliminating the need for separate control systems. This reduces overall device complexity while maintaining the adaptability benefits of multiple work modes.
Solution Approach 2:
The patent implements merging by combining the mode selection functionality with the speed control functionality in a single integrated control system. The mode selector and control unit work as a unified system where mode selection automatically triggers the appropriate speed parameter settings. This integration simplifies the control architecture compared to having separate independent control systems for different functions.
3Reliability
If the vehicle speed control target value is calculated based on blade rotation speed, then the protection of the work device is improved, but the productivity deteriorates because the vehicle speed is restricted beyond what is needed for safe operation
Solution Approach 1:
The patent applies parameter changes by providing multiple sets of speed limit parameters corresponding to different work modes. Each mode has optimized parameter values that balance device protection with travel efficiency. The control unit can select appropriate parameter sets based on the work situation, allowing higher vehicle speeds in modes where device protection is less critical while maintaining protective limits in modes where device safety is prioritized.
Data Source
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AI summary
An electric work vehicle includes: a control unit (5) including: a mode selector (57) configured to select a work mode to be applied from among a plurality of work modes each defining a rotation speed for the work device relative to the vehicle speed; a control target value calculator (58) configured to, based on an amount of operation of the vehicle speed manual operation tool (17) and the work mode having been selected, calculate a vehicle speed target value for the travel electric motor and a rotation speed target value for the work electric motor; a travel controller (52) configured to control the travel electric motor based on the vehicle speed target value; and a work controller (53) configured to control the work electric motor based on the rotation speed target value.