Swashplate Angle Control in Hydrostatic Pumps
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Solution Overview
Problem
Precise control of the swashplate angle in axial piston hydraulic pumps is challenging, particularly in zero turn vehicles, to achieve smooth straight-line travel and precise turning, while maintaining operator feel and cost-effectiveness.
Innovation Solution
A hydraulic pump control system that includes an electric motor connected to the swashplate, an electrical controller, an angle sensor, and a mechanical displacement amplifier to amplify tilting displacement, allowing for precise control of the swashplate angle through electrical command signals and operator input, enhancing the accuracy and resolution of angular displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct electrical control of swashplate angle is implemented, then control precision is improved, but operator feel characteristics deteriorate
Solution Approach 1:
A torque amplifier mechanism is introduced as an intermediary between the electrical motor and the swashplate. This mechanical intermediary provides operator feel characteristics by allowing the operator to sense and apply torque manually, while the motor provides precise electrical control signals to achieve accurate swashplate angle positioning without direct electrical actuation of the swashplate itself.
2Measurement precision
If mechanical displacement amplifier is added to amplify swashplate tilting displacement, then measurement resolution is improved, but device complexity increases
Solution Approach 1:
The torque amplifier and displacement amplifier functions are merged into a single integrated mechanical mechanism. This combined mechanism simultaneously provides torque multiplication for operator feel and displacement amplification for improved angular resolution, eliminating the need for separate amplifier components and reducing overall system complexity.
3Adaptability or versatility
If multiple control inputs are integrated in electrical controller, then control versatility is improved, but control system complexity increases
Solution Approach 1:
The electrical controller is designed with multi-functionality to handle multiple input types (manual torque input, electrical signals from various sensors and control systems) through a unified control architecture. This universal controller processes all inputs and generates appropriate motor control signals, providing versatile control capabilities while maintaining a relatively simple single-unit structure rather than multiple separate control devices.
Data Source
AI summary
A zero turn mower vehicle 10 includes left and right hydrostatic transmissions 11a, 11b driving wheels 15a, 15b. The transmissions 11a, 11b each include a swashplate type axial piston hydraulic pump 17 having a swashplate 22. A system 12 and method controls each pump 17. A controller 31 receives input signals and provides output signals to electric motors 33a, 33b to control each swashplate 22. Operator interface input devices 30a, 30b provide inputs to controller 31. Angle sensors 35a, 35b provide additional inputs to controller 31. Displacement amplifiers 36a, 36b amplify displacement of each swashplate 22, and torque amplifiers 34a, 34b amplify torque of electric motors 33a, 33b.