Variable Steering Reaction Force for Forklift Turn Return
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Solution Overview
Problem
Operators of forklifts face significant burden during steering operations, particularly when reversing the steering direction in the second-half of a turn, due to the wide steering angle range and the need for rapid steering actions, which can lead to accidental contact if the steering member return is delayed.
Innovation Solution
A vehicle steering system that computes the turning angle based on yaw angle changes and increases the steering reaction force when the angle exceeds a reference angle, assisting the operator in quickly directing the vehicle straight ahead by adjusting the gain of the reaction force motor during the second-half of a turn.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the steering reaction force is kept small at initial steering angles to allow smooth turning initiation, then the ease of operation is improved, but the productivity deteriorates because the operator cannot quickly return the steering member in the second-half of a turn
Solution Approach 1:
The patent applies dynamics by making the steering reaction force variable rather than constant. The reaction force control device dynamically adjusts the magnitude of reaction force based on the steering angle, providing small force at initial angles for smooth operation and large force at larger angles for rapid steering member return, thus resolving the contradiction between ease of operation and productivity
Solution Approach 2:
The patent changes the parameter of reaction force magnitude based on steering angle conditions. By establishing different reaction force characteristics for different steering angle ranges (small angle vs. large angle), the system optimizes both operational smoothness and return speed, addressing the contradiction between ease of operation and productivity
2Productivity
If the steering reaction force is increased to assist rapid steering member return in the second-half of a turn, then the productivity is improved, but the ease of operation deteriorates because the operator experiences excessive reaction force during normal steering
Solution Approach 1:
The system dynamically adjusts reaction force magnitude based on real-time steering angle feedback. The reaction force control device activates enhanced reaction force only when the steering angle exceeds a predetermined threshold, ensuring productivity improvement without compromising ease of operation during normal steering conditions
Solution Approach 2:
The patent applies local quality by providing different reaction force characteristics for different steering angle regions. The enhanced reaction force assistance is localized to the specific condition of large steering angles (second-half of turn), while normal steering operations maintain comfortable force levels, resolving the contradiction between productivity and ease of operation
3Adaptability or versatility
If the steering angle range is made wide to accommodate various turning requirements, then the adaptability is improved, but the difficulty of operation increases because the operator must perform large steering operations
Solution Approach 1:
The patent employs feedback by continuously monitoring the steering angle and using this information to adjust the reaction force magnitude. The reaction force control device receives steering angle signals and dynamically modifies reaction force output, providing assistance proportional to the steering demand, thus making wide steering angle operations easier while maintaining adaptability
Solution Approach 2:
The system changes the reaction force parameter based on steering angle magnitude. By establishing a relationship where reaction force increases with steering angle up to a threshold and then provides enhanced assistance beyond the threshold, the system accommodates wide turning requirements while reducing operator effort through adaptive force modulation
Data Source
AI summary
A steering angle detecting unit, a reaction force actuator that applies steering reaction force to a steering member, a yaw angle detecting unit that detects a yaw angle of a vehicle body, and a reaction force actuator control unit that sets the steering reaction force as a function of a steering angle and that controls the reaction force actuator such that the reaction force actuator generates the set steering reaction force, are provided. The reaction force actuator control unit computes a turning angle of the vehicle body on the basis of a change in the yaw angle of the vehicle body, detected by the yaw angle detecting unit. When the computed turning angle is larger than or equal to a reference angle, the steering reaction force applied to the steering member is increased.