Three-Wheeled Truck Steering and Drive Control
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Solution Overview
Problem
Traditional three-wheeled load-carrying trucks with a single rear wheel experience undesirable torque steering during acceleration and exaggerated turning effects during braking, due to the lack of braking on smaller front wheels, leading to instability and reduced traction.
Innovation Solution
The implementation of a load-carrying truck with at least one steerable and driven front wheel and a steerable rear wheel, utilizing an electrical motor control system that adjusts wheel speeds proportionally to wheel diameters and steering angles to maintain traction in both forward/reverse and sideways modes, ensuring that each driven wheel operates effectively during turns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single rear wheel is used for driving and braking, then the truck structure is simple, but torque steering occurs during acceleration and exaggerated turning effects occur during braking
Solution Approach 1:
The drive system is segmented into multiple independent wheel motors (front wheel motor and rear wheel motor) that can operate independently. This allows separate control of each wheel's torque and speed, eliminating the torque steering and exaggerated turning effects that occur with a single rear wheel drive system, while maintaining structural simplicity through modular motor units.
Solution Approach 2:
Different wheels are assigned different functions and characteristics: the front wheel has both steering and drive capabilities with its own motor, while the rear wheel provides additional drive support. This local differentiation of wheel qualities allows the front wheel to be steered independently during acceleration and braking, preventing torque steering, while the rear wheel provides stable propulsion.
2Volume of moving object
If the front wheel is made smaller to keep the load platform low, then storage space is maximized, but the front wheel lacks sufficient braking capability
Solution Approach 1:
The mechanical braking system is replaced with an electrical control system. Each wheel has its own motor that can provide electromagnetic braking by reversing torque direction. This substitution allows the small front wheel to have sufficient braking capability through electrical torque control rather than relying solely on mechanical brake size, maintaining compact platform height while ensuring reliable braking performance.
Solution Approach 2:
The braking capability is changed from a mechanical parameter (brake size) to an electrical parameter (motor torque control). By controlling the motor torque parameter, the small front wheel can generate adequate braking force without increasing its physical size, thus maintaining low platform height for maximum storage space while achieving reliable braking performance.
3Ease of operation
If motor speeds and torques are varied during turning, then steering control is achieved, but traction is lost due to wheel slip
Solution Approach 1:
The control system incorporates feedback from wheel speed sensors and steering angle sensors to continuously monitor wheel slip conditions and steering position. Based on this feedback, the controller dynamically adjusts motor speeds and torques to maintain optimal traction during turning maneuvers, preventing wheel slip while achieving smooth steering control.
Solution Approach 2:
The system dynamically adjusts motor parameters during turning operations. The front wheel motor speed and torque are varied based on steering angle and wheel slip detection, while the rear wheel motor provides compensating torque to maintain traction. This dynamic coordination of multiple motor parameters enables effective steering control without losing traction during turns.
Data Source
AI summary
A load-carrying truck has a fork lift mechanism mounted on a chassis, a pair of front wheels (24, 26) and a single rear wheel (30). At least one front wheel (26) and the rear wheel (30) are driven wheels whose speed is varied relative to one another differently depending on whether the truck is being driven in a forward reverse mode with the front wheels (24, 26) aligned generally parallel to the front-rear axis of the chassis and with steering controlled by steering the rear wheel (30), or a sideways mode with the rear wheel (30) aligned generally perpendicular to the front-rear axis of the chassis and with steering controlled by steering the at least one of the front wheels (26). When the truck is operated in forward/reverse mode and is steered towards the side on which the driven front wheel (26) is located, the relative speed (26) of that wheel is decreased progressively and comes to a stop when the axis of rotation of the rear wheel (30) intersects the front wheel position, and is driven in reverse at increasing speeds as the axis of the rear wheel (30) passes that point of intersection with further increasing steering angle. In the sideways mode of operation when the truck is steered in the direction towards the rear end of the chassis, the relative speed of the rear wheel (30) is decreased progressively and comes to a stop when the axis of rotation of the steered front wheel (26) intersects the rear wheel position, and the rear wheel (30) is driven in reverse at increasing speeds as the axis of the steered front wheel (26) passes said point of intersection with further increasing steering angle.