Joystick Force Feedback for Wheel Loaders
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Solution Overview
Problem
Operators of work vehicles, such as articulated vehicles and forklifts, cannot feel loads generated in hydraulic actuators during steering operations, leading to potential hindrance and unsafe maneuvers due to the lack of feedback on applied forces.
Innovation Solution
A work vehicle system comprising hydraulic actuators, a control valve, an operation member, a pressure sensor, and a controller that generates resistance to the operation member based on pressure differences sensed by the pressure sensor, allowing the operator to feel loads and obstacles during steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a spring member is used to generate counterforce at the joystick lever, then the steering operation is simplified, but the operator cannot feel the load generated in the hydraulic actuator
Solution Approach 1:
The patent introduces a feedback mechanism where the counterforce generation unit receives information about the hydraulic actuator's load and adjusts the counterforce applied to the joystick lever accordingly. This allows the operator to feel the load through the lever while maintaining easy operation, directly resolving the contradiction between operational simplicity and load feedback.
2Force
If hydraulic pressure is used to vary steering angle, then light operating force is sufficient, but the operator cannot feel obstacles or loads during steering
Solution Approach 1:
The patent introduces an intermediary system (counterforce generation unit) that mediates between the hydraulic actuator and the joystick lever. This intermediary translates the hydraulic load into a tactile counterforce that the operator can feel, while the actual steering still benefits from hydraulic assistance requiring minimal operating force.
3Measurement precision
If pilot pressure controls the steering valve, then precise steering control is achieved, but the operator loses awareness of hydraulic load
Solution Approach 1:
The system maintains precise pilot pressure control for accurate steering while simultaneously implementing feedback that informs the operator about hydraulic load conditions. The counterforce generation unit adjusts based on hydraulic actuator load, providing awareness without interfering with the precision of pilot pressure control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enables operators to safely navigate by providing tactile feedback of loads and obstacles, preventing impossible operations and enhancing control by varying resistance according to pressure differences and vehicle conditions.
Implementation Method 1
a pressure sensor which senses pressure values of the hydraulic actuators
Implementation Method 2
two hydraulic actuators which are disposed to the left and right of the linking shaft in a vehicle width direction and vary the steering angle of the front frame with respect to the rear frame
Implementation Method 3
a force imparting component which imparts an assisting force or a counterforce to the operation of the operation member
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A wheel loader (1) comprises steering cylinders (21, 22), a pilot valve (42), a joystick lever (24), a pressure sensor (29), a force imparting component (27), and a controller (28). The pilot valve (42) is configured to control the flow of fluid supplied to the steering cylinders (21, 22). The joystick lever (24) is operated by an operator when varying the steering angle (θs), and controls the pilot valve (42). The pressure sensing unit (29) is configured to sense the pressure generated by the steering cylinders (21, 22). The force imparting component (27) is configured to impart an assisting force or a counterforce to the operation of the joystick lever (24). The controller (28) is configured to control the force imparting component (27) so as to generate resistance against the operation of the joystick lever (24) on the basis of the pressure value detected by the pressure sensing unit (29).