Steerable Vehicle Dual Servomechanism Steering Control
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Solution Overview
Problem
Heavy self-propelled vehicles, such as agricultural tractors, face challenges with existing power steering systems that do not provide adequate self-centring and adjustable steering characteristics, particularly in off-road conditions, where furrows and uneven terrain override mechanical self-centring effects, making it difficult for drivers to maintain consistent steering angles.
Innovation Solution
A steerable vehicle equipped with a dual steering servomechanism system, comprising a hydraulic servomechanism for constant assistance and an electric servomechanism for adjustable torque, controlled by a programmable controller and human-machine interface, allowing for various steering modes and assistance levels to suit different operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hydraulic servomechanism is used for power steering assistance, then steering effort is reduced and steering becomes light, but self-centring characteristic is not provided
Solution Approach 1:
The patent combines a hydraulic servomechanism (for power assistance) with a self-centring mechanism into a single integrated steering system. The hydraulic cylinder incorporates both the assist function and the self-centring function, where the piston rod connects to the steering linkage and the hydraulic pressure automatically centers the piston when steering input is released, providing both light steering and self-centring characteristics simultaneously.
Solution Approach 2:
The hydraulic cylinder is designed to perform multiple functions: it provides power steering assistance to reduce steering effort, and simultaneously provides self-centring characteristic through its hydraulic design. The single component serves dual purposes, eliminating the need for separate mechanisms for each function.
2Stability of the object's composition
If positive caster angle is used for mechanical self-centring, then directional stability is improved on metalled roads, but self-centring effect is overridden by furrows and uneven terrain in off-road conditions
Solution Approach 1:
The patent replaces the mechanical self-centring mechanism (positive caster angle) with a hydraulic self-centring mechanism. Instead of relying on mechanical geometry that gets overridden by terrain irregularities, the system uses hydraulic pressure to provide self-centring force. The hydraulic fluid transmits force smoothly, allowing the self-centring effect to persist even when wheels encounter furrows and uneven off-road terrain.
Solution Approach 2:
The patent uses hydraulic pressure within the servomechanism to provide the self-centring effect. The hydraulic system can maintain consistent self-centring force regardless of external terrain conditions, as the hydraulic fluid pressure is controlled internally and not directly affected by external mechanical disturbances from furrows or uneven surfaces.
3Stability of the object's composition
If continuous steering input adjustments are made to overcome self-centring effect, then consistent steering angle is maintained, but driver convenience deteriorates and operation complexity increases
Solution Approach 1:
The hydraulic servomechanism is designed to automatically center the steering wheel itself without requiring continuous driver input adjustments. When the driver releases the steering wheel, the hydraulic system automatically returns the piston to its centered position, which in turn centers the steering wheel, maintaining consistent steering angle without driver intervention.
4Adaptability or versatility
If dual steering servomechanism system is implemented with multiple steering modes, then adaptability to different operating conditions is improved, but device complexity increases
Solution Approach 1:
The patent implements a dynamic steering system where the characteristics of the hydraulic servomechanism can be adjusted based on operating conditions. The system can modify steering assistance levels and self-centring characteristics dynamically, allowing adaptation to different terrains and operational requirements without requiring completely separate mechanical systems for each condition.
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
Enables flexible steering modes and assistance levels, improving driver convenience and vehicle stability by allowing self-centring, damping, and effortless steering, adapting to on-road and off-road conditions, and enabling remote guidance and autonomous operation.
Implementation Method 1
a pump for pressurising a fluid such as hydraulic oil in a circuit that includes a servovalve
Implementation Method 2
an electric motor that is connected to provide rotational assistance forces to the steering column
Data Source
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AI summary
A steerable, self-propelled vehicle (20) includes a rotatable steering column (21) that is connected to control the steering angle of one or more ground-engaging members (26) of the vehicle. The vehicle includes between the steering column and the ground-engaging member a first steering servomechanism having at least a first steering assistance characteristic; a second steering servomechanism having a second steering assistance characteristic also being connected to act on the steering column (21). A controller (41) is provided for causing the first and second steering assistance characteristics to influence the steering of the vehicle (20) in dependence on one or more one or more control commands generated in the controller (41).