Forklift Steer-by-Wire Ball Screw Control Against Over-Stroking
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Solution Overview
Problem
Hydraulic steering systems in vehicles are inefficient due to power loss, low resolution, and require frequent maintenance, while existing electric steer-by-wire systems lack accuracy and durability.
Innovation Solution
A steer-by-wire control system with a steering assembly, actuator, and controller that uses a ball screw nut and rotor to precisely control steered wheels, incorporating a tactile feedback device and resistance force to prevent over-stroking, and a controller that limits angular movement within a preset range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic systems are used for steering, then reliability is improved, but energy efficiency deteriorates due to power loss
Solution Approach 1:
The patent replaces the hydraulic mechanical system with an electric motor-driven ball screw mechanism. The electric actuator converts electrical energy to mechanical rotation, which the ball screw converts to linear motion for steering control, eliminating hydraulic fluid power transmission and associated energy losses.
Solution Approach 2:
The patent explicitly eliminates the hydraulic system by using an electric actuator with a ball screw mechanism instead. This substitution removes the need for hydraulic pumps, valves, and fluid power transmission, directly addressing the energy efficiency problem while maintaining steering reliability.
2Duration of action of stationary object
If hydraulic systems are used for steering, then durability is improved, but maintenance frequency increases
Solution Approach 1:
The patent replaces the complex hydraulic system with a simplified electric actuator and ball screw mechanism. This electric system has fewer moving parts, no hydraulic seals to leak, and no fluid to degrade, thereby improving durability while reducing maintenance requirements.
Solution Approach 2:
The ball screw mechanism provides self-lubrication through its threaded geometry and inherent friction characteristics, reducing the need for external maintenance. The system is designed to operate reliably with minimal intervention, allowing it to serve itself regarding basic lubrication and adjustment.
3Loss of energy
If electric actuators are used in steer-by-wire systems, then energy efficiency is improved, but steering accuracy deteriorates
Solution Approach 1:
The patent uses an electric motor with encoder feedback to control the ball screw actuator. The encoder provides precise positional feedback to the controller, enabling accurate steering angle control despite the electric actuation method, thereby resolving the accuracy concern.
Solution Approach 2:
The patent incorporates feedback mechanisms including the encoder on the electric motor and position sensors on the ball screw assembly. This feedback allows the controller to monitor and adjust the steering actuator position in real-time, ensuring accurate steering control while maintaining energy efficiency.
4Ease of repair
If electric actuators are used in steer-by-wire systems, then maintenance needs are reduced, but durability deteriorates
Solution Approach 1:
The patent replaces hydraulic components with an electric motor and ball screw mechanism that has inherently fewer failure points. The ball screw provides rigid mechanical support and precise positioning, while the electric motor offers controlled operation, together creating a more durable system requiring less maintenance.
Solution Approach 2:
The ball screw mechanism is designed to be self-lubricating and self-supporting, reducing maintenance needs. The rigid mechanical structure provides inherent durability without requiring frequent intervention, allowing the system to maintain itself over extended operation periods.
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 provides accurate and durable steering control, preventing over-stroking and maintaining efficiency by limiting angular movement, thus enhancing vehicle maneuverability and reducing maintenance needs.
Implementation Method 1
The ball screw nut is configured to rotate about an axis to cause the actuator rod to translate axially along the axis relative to the ball screw nut
Data Source
AI summary
A steer-by-wire control system adapted for use with a material handling vehicle such as a forklift includes a controller programmed to receive input indicative of a desired direction of travel of the material handling vehicle and to control an actuator coupled with the steered wheels of the material handling vehicle to change the direction of travel of the vehicle.