"a vehicle rear-wheel steering system and its method of operation"

Abstract

The vehicle rear-wheel steering system (200) comprises of a controller (10), a front steering sensor (20), a rear steering sensor (30), an application switch 1 parallel steer (40), an application switch 2 opposite steer (50), a H bridge forward +ve relay (60), a H bridge forward -ve relay (70), a H bridge reverse +ve relay (80), a H bridge forward -ve relay (90), and a motor (100). The present invention optimises stability, manoeuvrability, and overall driving experience in different driving conditions, allows for tighter turns and reduced turning radii, is adaptable to the different steering demands imposed upon it by the driver in varying driving conditions, is precise and highly responsive to steering demands imposed on it by the vehicle operator, can be provided within existing vehicles with minimum changes, and is economical to provide in existing vehicles.

Description

“A VEHICLE REAR-WHEEL STEERING SYSTEM AND ITS METHOD OF OPERATION”Field of Invention

[0001] The invention relates to the steering system provided in light commercial vehicles. It more particularly relates to steering systems that are provided with electrical mechanisms, controlled through electronic means, to assist the driver in turning the wheels.Background of the Invention

[0002] Traditional vehicles lack independent rear-wheel steering control, limiting manoeuvrability and stability. This also makes it essential for drivers of such vehicles to receive extensive driver training to perform all critical driving manoeuvres using only the front steering controls. In the same logical flow, it can also be stated that human errors may also be introduced for any number of reasons, thereby affecting safety and increasing operation and maintenance costs due to non-optimal use of the light commercial vehicle. The need for a well-tailored system that can accurately steer the rear wheels, thereby significantly enhancing vehicle stability and manoeuvrability during driving, has been, for this reason, a long-felt but unfulfilled need of the industry.

[0003] Exiting means for steering the vehicle also doesn’t satisfactorily account for the need for aligning the rear wheels parallelly with the front wheels, or alternatively, aligning them in the opposite direction to that of the front wheels at the right moment by making an intelligent determination of the existence of the need for performance of such actions while the vehicle is being driven. Situations demanding the performance of such manoeuvres can emerge on a daily basis in a typical working day for the drivers of light commercial vehicles. Depending only on vehicles having only front wheel steering, even when they are being operated by trained manpower, dealing with such manoeuvrability requirements may not always be possible. The existing front-wheel steered commercial vehicles, even those that have been provided with ESC, traction control, ABS, and power steering, struggle to meet such precise manoeuvrability requirements. In simple and straightforward terms, the challenge pertains to fulfilling the stability and manoeuvrability requirements of the light commercial vehicle across diverse and dynamic driving conditions, utilising only moderately skilled drivers.

[0004] An ideal solution to such a problem would have to use existing vehicle architecture to remain economical. Therefore, the ideal solution also has to be compatible, interoperable, and integrable with existing light commercial vehicles with the bare minimum of changes. Furthermore, to allow such vehicles to remain current with the requirement of driving needs of their typical operators, they would also have to be capable of adapting to permit dynamic adjusted steering behaviour based on driving conditions, vehicle speed, and other parameters, ensuring optimal performance across a range of scenarios. By adapting to changing conditions, the ideal system would optimise vehicle handling and responsiveness, thereby enhancing the overall driving experience. There are no known steering systems capable of fulfilling such a diverse range of requirements. Therefore, the present invention aims to provide a vehicle rear-wheel steering system with CAN bus communication and parallel opposite steering modes that optimise stability, manoeuvrability, and overall driving experience in different driving conditions.

[0005] It is another objective of the present invention is to provide a vehicle rearwheel steering system and its method of operation, that allows for tighter turns and reduced turning radii.

[0006] It is still another objective of the present invention to provide a vehicle rearwheel steering system and its method of operation that is adaptable to the different steering demands imposed upon it by the driver in varying driving conditions.

[0007] It is yet another objective of the present invention to provide a vehicle rearwheel steering system and its method of operation that is precise and highly responsive to steering demands imposed on it by the vehicle operator.

[0008] It is another objective of the present invention to provide a vehicle rearwheel steering system and its method of operation, that can be provided within existing vehicles with minimum changes.

[0009] It is yet another objective of the present invention to provide a vehicle rearwheel steering system and its method of operation that is economical to provide in existing vehicles.Summary of the Invention

[0010] The disclosed invention achieving the stated objectives i.e. the vehicle rearwheel steering system (200) which comprises of a controller, a front steering sensor, a rear steering sensor, an application switch 1 parallel steer, an application switch 2opposite steer, a H bridge forward +ve relay, a H bridge forward -ve relay, a H bridge reverse +ve relay, a H bridge forward -ve relay, and a motor. In the vehicle rear-wheel steering system as disclosed, the controller is electrically connected with the front steering sensor, the rear steering sensor, the application switch 1 parallel steer, the application switch 2 opposite steer, the H bridge forward +ve relay, the H bridge forward -ve relay, the H bridge reverse +ve relay, and the H bridge forward -ve relay. The H bridge forward +ve relay, and the H bridge forward -ve relay are together electrically connected with one terminal of the motor; and the H bridge reverse +ve relay, and the H bridge forward -ve relay are together electrically connected with the other terminal of the motor.Brief Description of Drawings

[0011] The present invention is illustrated in the accompanying drawings. The description of the present invention would, therefore, be better understood with reference to accompanying diagrams, wherein

[0012] Figure 1 discloses a schematic diagram of the system in accordance with the present invention.

[0013] Figure 2 discloses a flow chart indicating the working method in accordance with the present invention.Detailed Description of the Invention

[0014] To achieve the stated objectives, a vehicle rear-wheel steering system (200) with CAN bus communication and parallel and opposite steering modes is disclosed.

[0015] Referring to figure 1 , it is stated that, a vehicle rear-wheel steering system (200) in accordance with the present invention comprises of a controller (10), a front steering sensor (20), a rear steering sensor (30), an application switch 1 parallel steer (40), an application switch 2 opposite steer (50), a H bridge forward +ve relay (60), a H bridge forward -ve relay (70), a H bridge reverse +ve relay (80), a H bridge forward -ve relay (90), and a motor (100).

[0016] In the vehicle rear-wheel steering system (200) in accordance with the present invention (refer to Fig. 1), the controller (10) is electrically connected with the front steering sensor (20), the rear steering sensor (30), the application switch 1 parallel steer (40), the application switch 2 opposite steer (50), the H bridge forward+ve relay (60), the H bridge forward -ve relay (70), the H bridge reverse +ve relay (80), and the H bridge forward -ve relay (90). The controller (10) is electrically connected to the front steering sensor (20), and the rear steering sensor (30) through an interface of the Control Area Network (CAN) that has been provided on the vehicle. The H bridge forward +ve relay (60), and the H bridge forward -ve relay (70) are together electrically connected with one terminal of the motor (100). The H bridge reverse +ve relay (80), and the H bridge forward -ve relay (90) are together electrically connected with the other terminal of the motor (100).

[0017] The method of operating the vehicle rear-wheel steering system (200) (refer to Fig. 2) has eleven steps that are executed by the controller (10) depending upon the inputs received through the CAN bus interface from the sensors mounted on the vehicle that include the front steering sensor (20) and the rear steering sensor (30). As a first step, when the vehicle is started by the operator, the vehicle rear-wheel system (200) is initialised as soon as it receives power. As a second step, after the vehicle rear-wheel system (200) is initialised, inputs signals from the front steering sensor (20), and the rear steering sensor (30) are read. As a third step, after the input signals from the front steering sensor (20), and the rear steering sensor (30) have been read, the controller (10) if the application switch 1 parallel steer (40) has been switched ON sets a parallel mode for operation, otherwise if the application switch 2 opposite steer (50) is switched ON the controller (10) sets an opposite mode for operation. The controller (10) can also select the parallel or opposite modes dynamically on its own. As a fourth step, after either parallel or opposite mode of operation has been set by the controller (10), said controller (10) calculates a desired rear wheel steering angle.

[0018] As a fifth step, after the controller (10) has calculated a desired rear wheel steering angle, the rear wheel position is read based on inputs from rear wheel sensor (30). As a sixth step, after the rear wheel position has been read by the controller (10), said controller (10) calculates an error ‘E’ in steering angle. As a seventh step, after the controller has calculated the error in steering angle, said controller (10) applies a control algorithm where, if the ‘E’ is greater than a threshold value said controller (10) issues a command to the H bridge relays (60, 70, 80, and 90) that in turn cause the motor (100) to be rotated in one direction thereby giving effect to a right steering command, if the if the ‘E’ is less than a negative threshold value said controller (10) issues a command to the H bridge relays (60, 70, 80, and 90) that in turn cause themotor (100) to be rotated in the other direction thereby giving effect to a left steering command, otherwise the controller (10) maintains current steering position without passing any signals to the H bridge relays (60, 70, 80, and 90) and causing operation of the motor (100).

[0019] As a eighth step, after the controller (10) has issued the commands for right or left steer or maintaining current steering position, the H bridge relays (60, 70, 80, and 90) give effect to the command from said controller (10). As an ninth step, after the H bridge relays (60, 70, 80, and 90) give effect to the command from said controller (10) to cause right, or left or for maintaining the current steering position, the motor (100) operates to execute the control action. As a tenth step, after the control action has been executed by operation of the motor (100), said controller (10) monitors the vehicle dynamics. As a eleventh step, after monitoring the vehicle dynamics said controller (10) continues to read input signals from the front steering sensor (20), and the rear steering sensor (30). The steps one to eleventh of the method of operation of the vehicle rear-wheel steering system (200) are sequentially executed by the controller (10).

[0020] The Relay-Controlled H-bridge mechanism (constituted by H bridge relays (60, 70, 80, and 90)), as provided in the present invention, as linked with the controller (10) (alternatively, also identifiable as ECU / control unit), is at the core of the schematic layout, as shown in Fig. 1. This mechanism is responsible for managing rear-wheel steering. It has relay switches that control the polarity of the motor connected to the rear wheels. By selectively activating these relays (the H bridge relays (60, 70, 80, and 90)), the system can dictate the direction of motor (100)’s rotation, thereby adjusting the steering angle of the rear wheels.

[0021] The Control Unit / ECU (alternatively, also identified as the controller (10) within this document) (refer Fig. 1), as provided in the present invention, and as linked with the Relay-Controlled H-bridge mechanism (constituted by H bridge relays (60, 70, 80, and 90)), the sensors (namely the front steering sensor (20), the rear steering sensor (30)), switches (namely the application switch 1 parallel steer (40) and the application switch 2 opposite steer (50)), and indirectly through said Relay-Controlled H-bridge mechanism (constituted by H bridge relays (60, 70, 80, and 90)) with the motor (100), serves as the brain of the system. The control unit (alternatively identified as controller (10) in this document) houses the software algorithms and processing capabilities necessary for steering control. This control unit (alternatively identified ascontroller (10) in this document) interprets input signals from the installed sensors and driver controls, executes adaptive control algorithms, and sends commands to the relay-controlled H-Bridge mechanism (constituted by H bridge relays (60, 70, 80, and 90)). It also communicates with other onboard systems through the vehicle's CAN bus interface.

[0022] Sensors (namely the front steering sensor (20) and the rear steering sensor (30)), as linked with the controller (10) (Refer Fig. 1), and as provided within the present invention, include angular sensors strategically placed at the steering column and rear rack to provide real-time feedback on rear-wheel position, and front-wheel steering angle. The controller (10) also receives inputs on vehicle speed, and other relevant parameters through other sensors mounted on the vehicle through the CAN nus interface. All of these sensors continuously monitor vehicle dynamics and relay data to the control unit, enabling accurate steering adjustments and mode selection.

[0023] CAN Bus Interface (refer to Fig. 1), as provided within the present invention, facilitates seamless integration with onboard vehicle systems; the control unit (alternatively identified as the controller (10)) features the CAN bus interface. This interface allows the control unit (alternatively identified as the controller (10)) to exchange control signals, sensor data, and diagnostic information with other vehicle systems, enabling centralised monitoring and control of rear-wheel steering functionality.

[0024] The present invention introduces a rear-wheel steering system for vehicles (200) featuring CAN bus communication for integration with onboard systems. The rear-wheel steering system for vehicles (200) incorporates relay-controlled H-Bridge (constituted by H bridge relays (60, 70, 80, and 90)) motor (100) polarity control, an operating mode algorithm (that further includes PWM signal modulation tuned by a PID algorithm), and distinct Parallel and Opposite Steering modes (selected by operation of the application switch 1 parallel steer (40) or the application switch 2 opposite steer (50) or dynamically by the controller (10)). This combination enhances vehicle stability, manoeuvrability, and control, offering versatile steering options for various driving scenarios.

[0025] The present invention that is the rear-wheel steering system for vehicles (200) integrates with the vehicle's CAN bus for seamless communication with onboard systems. This rear-wheel steering system for vehicles (200) includes the relay- controlled H-Bridge (constituted by H bridge relays (60, 70, 80, and 90)) motor (100)polarity control, an operating mode algorithm (that further includes PWM signal modulation tuned by a PID algorithm), and distinct Parallel and Opposite Steering modes (selected by operation of the application switch 1 parallel steer (40) or the application switch 2 opposite steer (50) or dynamically by the controller (10) during the vehicles operation), providing enhanced vehicle stability, manoeuvrability, and control across diverse driving conditions.

[0026] The relay-controlled H-Bridge mechanism (constituted by H bridge relays (60, 70, 80, and 90)) serves as the core component for managing motor (100)’s polarity, ensuring efficient and reliable control of rear-wheel steering. By receiving control signals via the CAN bus, the rear-wheel steering system for vehicles (200) selectively activates relay switches (the H bridge relays (60, 70, 80, and 90)) to regulate motor (100)’s direction, facilitating precise adjustments to the rear-wheel steering angle.

[0027] In addition to motor (100)’s polarity control, the rear-wheel steering system for vehicles (200) utilises PWM signal modulation for motor (100)’s speed control. The PWM signal (from the controller (10)), fine-tuned by a PID algorithm (at the controller (10)), and transmitted through the electrical connection through the CAN bus interface (see ‘CAN’ in Figure 1), adjusts the duty cycle based on feedback from sensors (namely the rear steering sensor (30) and the front steering sensor (20)) monitoring rear-wheel position and front-wheel steering angle. The rear-wheel steering system for vehicles (200) is a closed-loop control mechanism that enables smooth and responsive steering adjustments, optimising vehicle handling dynamics.

[0028] The methods, as executable through the rear-wheel steering system for vehicles (200), include the method of operation enabled by a PID Algorithm and the systematic method of operation facilitated by the operating mode algorithm. PID Algorithm is responsible for tuning the Pulse Width Modulation (PWM) signal used to drive the rear-wheel steering motor. The PID algorithm continuously adjusts the PWM signal based on feedback (received through the CAN bus interface) from sensors (namely the rear steering sensor (30) and the front steering sensor (20)) monitoring rear-wheel position and front-wheel steering angle, ensuring precise alignment and responsiveness.

[0029] Moreover, the rear-wheel steering system for vehicles (200) incorporates the operating mode algorithm that dynamically selects between two distinct rearwheel steering modes: Parallel and Opposite Steering. The Operating Mode Algorithmenables the dynamically selection between Parallel and Opposite Steering modes (by the controller (10)) based on driving conditions and user inputs (as received through the CAN bus interface and also from the application switch 1 parallel steer (40) and the application switch 2 opposite steer (50)). This algorithm optimizes steering behaviour for stability at high speeds and manoeuvrability at low speeds. This selection can also be affected by the operation of the application switch 1 parallel steer (40) or the application switch 2 opposite steer (50).

[0030] The parallel steering mode: Optimised for stability at higher speeds, the Parallel Steering mode ensures that the rear wheels track in parallel with the front wheels. This mode enhances vehicle stability during straight-line driving and highspeed manoeuvres, reducing the risk of oversteering and improving overall handling characteristics.

[0031] The opposite steering mode: Geared towards enhanced manoeuvrability at lower speeds, the Opposite Steering mode steers the rear wheels in the opposite direction to the front wheels. This mode facilitates tighter turning radii, making parking and low-speed manoeuvres more manageable and reducing the vehicle's turning circle.

[0032] The integration of CAN bus communication enables seamless interaction and data exchange between the rear-wheel steering system for vehicles (200) and other onboard vehicle systems. Control signals, sensor data, and diagnostic information are transmitted and received over the CAN bus, allowing for centralised monitoring and control of rear-wheel steering functionality by the controller (10).

[0033] The vehicle rear-wheel steering system for vehicle (200)’s method of operation follows the flow chart disclosed in Fig. 2. The vehicle rear-wheel steering system for vehicles (200), and its method of operation (refer to Figs. 1 & 2) enables independent control of rear-wheel steering using relay-controlled H-Bridge mechanism (constituted by H bridge relays (60, 70, 80, and 90)) and advanced software algorithms. It offers dynamic Parallel and Opposite Steering modes, optimising stability and manoeuvrability across various scenarios; utilises closed-loop feedback control system with sensors for real-time monitoring and precise adjustments. It also provides for seamlessly integration with the vehicle's CAN bus, allowing for centralised control and communication with other systems. It employs adaptive algorithms like PID for PWM modulation and mode selection, optimising performance in different situations. It also offers versatility through multiple steeringmodes and adaptability to different driving scenarios and environmental factors; and provides precise and responsive steering control, enhancing vehicle handling and driver confidence.

[0034] The novel features of the vehicle rear-wheel steering system for vehicles (200) and its method of operation are: a. Autonomous Rear-Wheel Steering: Unlike conventional setups that rely solely on front-wheel steering, this innovation allows for independent control of the rear wheels. This capability enables precise adjustments to the rear-wheel steering angle, enhancing vehicle stability and manoeuvrability, especially during highspeed manoeuvres and tight turns. b. Dynamic Steering Modes: This innovation introduces two distinct steering modes: Parallel and Opposite Steering. In Parallel Steering mode, the rear wheels align with the front wheels to improve stability at higher speeds, while the Opposite Steering mode positions the rear wheels in the opposite direction for enhanced manoeuvrability during lower-speed scenarios. This flexibility optimises steering behaviour across diverse driving conditions. c. Continuous Feedback Control: The system incorporates a closed-loop feedback mechanism that continuously monitors rear-wheel position and front-wheel steering angle through sensors. This real-time feedback enables precise steering adjustments, ensuring alignment with the front wheels and responsive handling. d. Seamless Integration with CAN Bus: Integrating with the vehicle's CAN bus allows for centralized control and communication with other onboard systems. This integration facilitates data exchange, centralized monitoring, and control of rearwheel steering functionality, enhancing overall vehicle performance and safety. e. Adaptive Control Algorithms: Employing adaptive control algorithms, including a PID algorithm for PWM modulation and an operating mode algorithm for mode selection, allows for dynamic adjustments to steering behaviour based on driving conditions, vehicle speed, and other parameters. f. Versatile Steering Options: Offering multiple steering modes and adaptive control algorithms, the innovation enhances vehicle versatility and adaptability. Drivers can select the appropriate steering mode based on driving conditions, optimizing stability, manoeuvrability, and overall driving experience.g. Precision Steering: With accurate rear-wheel steering adjustments, this innovation ensures precise and responsive vehicle control, enhancing vehicle handling dynamics and driver confidence across various driving scenarios.

[0035] The vehicle rear-wheel steering system for vehicles (200) and its method of operation, in accordance with the present invention, achieve all the stated objectives.

[0036] Technical advantages offered by the invention, i.e. , the vehicle rear-wheel steering system for vehicles (200) and its method of operation, are that-It optimises stability, manoeuvrability, and overall driving experience in different driving conditions.It allows for tighter turns and reduced turning radii.It is adaptable to the different steering demands imposed upon it by the driver in varying driving conditions.It is precise and highly responsive to steering demands imposed on it by the vehicle operator.It can be provided within existing vehicles with minimum changes.It is economical to provide in existing vehicles.

[0037] It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the present invention has been herein described in terms of its preferred embodiment, those skilled in the art will recognise that the preferred embodiment herein disclosed can be practised with modifications within the scope of the invention herein described.Dated 27 June 2024

Claims

CLAIMSWe Claim,1. A vehicle rear-wheel steering system (200) comprising of• a controller (10),• a front steering sensor (20),• a rear steering sensor (30),• an application switch 1 parallel steer (40),• an application switch 2 opposite steer (50),• a H bridge forward +ve relay (60),• a H bridge forward -ve relay (70),• a H bridge reverse +ve relay (80),• a H bridge forward -ve relay (90),• a motor (100), wherein,- the controller (10) is electrically connected with the front steering sensor (20), the rear steering sensor (30), the application switch 1 parallel steer (40), the application switch 2 opposite steer (50), the H bridge forward +ve relay (60), the H bridge forward -ve relay (70), the H bridge reverse +ve relay (80), and the H bridge forward -ve relay (90);- the H bridge forward +ve relay (60), and the H bridge forward -ve relay (70) are together electrically connected with one terminal of the motor (100); and- the H bridge reverse +ve relay (80), and the H bridge forward -ve relay (90) are together electrically connected with the other terminal of the motor (100).

2. The vehicle rear-wheel steering system (200) as claimed in claim 1, wherein the controller (10) is electrically connected to the front steering sensor (20), and the rear steering sensor (30) and vehicle mounted sensors for speed through an interface of the Control Area Network (CAN) that has been provided on the vehicle.

3. The method of operating the vehicle rear-wheel steering system (200) as claimed in Claim 2, whereinas a first step, when the vehicle is started by the operator, the vehicle rear-wheel system (200) is initialised as soon as it receives power; as a second step, after the vehicle rear-wheel system (200) is initialised, inputs signals from the front steering sensor (20), and the rear steering sensor (30) are read; as a third step, after the input signals from the front steering sensor (20), and the rear steering sensor (30) have been read, the controller (10) if the application switch 1 parallel steer (40) has been switched ON sets a parallel mode for operation, otherwise if the application switch 2 opposite steer (50) is switched ON the controller (10) sets an opposite mode for operation, the controller (10) can also select the modes dynamically on its own; as a fourth step, after either parallel or opposite mode of operation has been set by the controller (10), said controller (10) calculates a desired rear wheel steering angle; as a fifth step, after the controller (10) has calculated a desired rear wheel steering angle, the rear wheel position is read based on inputs from rear wheel sensor (30); as a sixth step, after the rear wheel position has been read by the controller (10), said controller (10) calculates an error ‘E’ in steering angle; as a seventh step, after the controller has calculated the error in steering angle, said controller (10) applies a control algorithm where, if the ‘E’ is greater than a threshold value said controller (10) issues a command to the H bridge relays (60, 70, 80, and 90) that in turn cause the motor (100) to be rotated in one direction thereby giving effect to a right steering command, if the if the ‘E’ is less than a negative threshold value said controller (10) issues a command to the H bridge relays (60, 70, 80, and 90) that in turn cause the motor (100) to be rotated in the other direction thereby giving effect to a left steering command, otherwise the controller (10) maintains current steering position without passing any signals to the H bridge relays (60, 70, 80, and 90) and causing operation of the motor (100); as a eighth step, after the controller (10) has issued the commands for right or left steer or maintaining current steering position, the H bridgerelays (60, 70, 80, and 90) give effect to the command from said controller (10); as an ninth step, after the H bridge relays (60, 70, 80, and 90) give effect to the command from said controller (10) to cause right, or left or for maintaining the current steering position, the motor (100) operates to execute the control action; as a tenth step, after the control action has been executed by operation of the motor (100), said controller (10) monitors the vehicle dynamics; and as a eleventh step, after monitoring the vehicle dynamics said controller (10) continues to read input signals from the front steering sensor (20), and the rear steering sensor (30).

4. The method of operating the vehicle rear-wheel steering system (200) as claimed in Claim 3, wherein, the steps one to eleven of the method of operation of the vehicle rear-wheel steering system (200) are sequentially executed by the controller (10).Dated 27 June 2024

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