Fail-operational steer-by-wire steering system

Abstract

A steering system includes an actuator to adjust a steering angle of the steering system and a primary electrical power source to provide a first flow of electrical power. A mechanical to electrical conversion device converts a mechanical steering input into a second flow of electrical power. Circuitry is configured to detect a fault the steering system and based on detection of the fault to switch operation of the steering system between a normal mode and a fail-operational mode. In the normal mode, the first flow of electrical power from the primary electrical power source causes the actuator to adjust the steering angle. In the fail-operational mode the second flow of electric power from the mechanical to electrical conversion device causes the actuator to adjust the steering angle.

Description

FAIL-OPERATIONAL STEER-BY-WIRE STEERING SYSTEMCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of US Provisional Application No. 63 / 548,827 filed on February 1, 2024, the contents of which are incorporated in its entirety.BACKGROUND

[0002] The present disclosure relates to fail-operational systems and methods for steer-by- wire systems. Such fail-operational systems may be used with hydraulic machines (e.g., loaders, excavators, etc.) as well as other steer-by-wire systems such as automobiles.SUMMARY

[0003] Steer-by-wire systems in the automotive industry have traditionally relied on hydraulic steering orbitrols or steering control units (SCUs) to amplify output hydraulic power based on steering wheel movement from the driver. These systems have been favored due to their high reliability and fail-safe operation, particularly in the event of a hydraulic or electrical power failure where the orbitrol can act as a pump to power the steering mechanism / cylinder to turn the steering axle(s). However, the introduction of steer-by-wire technology' has presented new possibilities for machine steering control and cab design, although its adoption has been limited due to the cost and complexity of implementing redundant systems and controllers to achieve the same level of fail-operational capability as traditional hydraulic only systems with SCU.

[0004] Aspects of the present disclosure provide a system, e.g.. a steer-by-wire system, that eliminates the need for such mechanical or electrical system redundancies by generating electrical power from user-input during steering. Thus, a steer-by-wire system according to the present disclosure can reduce mechanically or electrically redundant parts in a steering system while still supporting fail-operational regulations. The foregoing and other aspects and advantages of the disclosure will appear from the following description. In the description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration a preferred configuration of the disclosure. Such configuration does not necessarily represent the full scope of the disclosure, however, and reference is made therefore to the claims and herein for interpreting the scope of the disclosure.

[0005] Aspects of the described technology' provide a steering system having a fail- operational mode of operation. The steering system may include an actuator to adjust a steering angle of the steering system. The system may further include a primary electrical power sourceto provide a first flow of electrical power, and a mechanical to electrical conversion device (i.e. generator) to convert a mechanical steering input power (torque * speed) into a second flow of electrical power. The steering system may further include circuitry to switch operation of the steering system based on detection of a fault. For example, the system may switch operation between a normal mode in which the first flow of electrical power from the primary electrical power source controlled by the controller causes the actuator to adjust the steering angle, and a fail-operational mode in which the second flow of electric power from the generator causes the actuator to adjust the steering angle.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The disclosure will be better understood, and features, aspects, and advantages will become apparent when consideration is given to the following detailed description thereof. Such detailed description references to the following drawings.

[0007] FIG. 1 illustrates an example fail-operational steer-by-wire system.

[0008] FIG. 2 illustrates a second example fail-operational steer-by-wire system.

[0009] FIG. 3A illustrates example direction detection via phase comparison.

[0010] FIG. 3B illustrates an example steering control circuit.

[0011] FIG. 4 illustrates an example vehicle including a fail-operational steer-by-wire system as described herein.

[0012] FIG. 5 illustrates another example vehicle having a fail-operational steer-by-wire steering system.

[0013] FIG. 6 illustrates another example vehicle having a fail-operational steer-by-wire steering system.

[0014] FIG. 7 illustrates another example vehicle having a fail-operational steer-by-wire steering system.

[0015] FIG. 8 illustrates another example vehicle having a fail-operational steer-by-wire steering system.

[0016] FIG. 9 illustrates an example fail -operational steering control circuit comprising a microprocessor and a secondary7steering control signal generator circuit.DETAILED DESCRIPTION

[0017] Disclosed embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all of the disclosed embodiments are shown. Indeed, several different embodiments may be provided and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so thatthis disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

[0018] The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected examples and are not intended to limit the scope of examples of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of examples of the disclosed technology.

[0019] Before any embodiments are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported.” and “coupled” and vanations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

[0020] Unless context indicates otherwise, the term “fluid” may include to any substance which behaves in a fluid manner and may include both gases (e.g., compressed air for a pneumatic system) and liquids (e.g., hydraulic fluid). Accordingly, examples described with respect to hydraulic systems may, unless indicated to the contrary, be implemented via pneumatic systems, and vice versa. The use of the terms “downstream” and “upstream” herein are terms that indicate direction relative to the flow of a fluid. The term “downstream” corresponds to the direction of fluid flow, while the term “upstream” refers to the direction opposite or against the direction of fluid flow7. As indicated by context, the term “power” may refer to rotational power (e.g., torque times rotational speed). Accordingly, where context indicates, torque and speed may be understood as synonymous with / directly related to e rotational power. For instance, the phrase “increasing torque” may, unless context indicates otherwise, refer to increasing torque while holding speed constant, thereby increasing rotational power.

[0021] As will be clear from context, signals and signal lines may in some cases be referred to using common reference numbers. Unless context dictates otherwise, in these cases, areference to “a signal TV” should be read as “a signal transmitted on a signal line TV”. For instance, the phrase such as "a circuit transmitting a control signal T” should be understood asc’a circuit X transmitting a control signal on a signal line IT.

[0022] In some implementations, devices or systems disclosed herein can be utilized, manufactured, or installed using methods embodying aspects of the described technology'. Correspondingly, any description herein of particular features, capabilities, or intended purposes of a device or system is generally intended to include disclosure of a method of using such devices for the intended purposes, a method of otherwise implementing such capabilities, a method of manufacturing relevant components of such a device or system (or the device or system as a whole), and a method of installing disclosed (or otherwise known) components to support such purposes or capabilities. Similarly, unless otherwise indicated or limited, discussion herein of any method of manufacturing or using for a particular device or system, including installing the device or system, is intended to inherently include disclosure, as embodiments, of the utilized features and implemented capabilities of such device or system.

[0023] Steering systems in the mobile off-highway industry have traditionally relied on hydraulic steering orbitrols or steering control units (SCUs) to provide hydraulic power based on steering wheel movement from the operator. These systems have been favoured due to their high reliability7and fail-operational operation, particularly in the event of a power failure where the orbitrol can act as a pump to turn the steering mechanism / cylinder. However, the introduction of steer-by-wire technology (Not having a fluidic connection between the operators steering wheel and axle via a SCU or similar) has presented new possibilities for steering control, although its adoption has been limited due to the cost and complexity of implementing redundant systems and controllers to achieve the same level of fail-operational capability’ as traditional hydraulic systems.

[0024] Aspects of the present disclosure provide a fault-tolerant system, e.g. , a steer-by-wire system, operated from electricity generated by user-input during steering in the event of a system electrical failure. Thus, a steer-by-wire system according to the present disclosure can reduce redundant parts in a steering system yvhile adhering to fail-operational regulations. The foregoing and other aspects and advantages of the disclosure will appear from the following description. In the description, reference is made to the accompanying drawings, which form a part hereof, and in which there is show n by way of illustration, preferred configurations of the disclosure. Such configurations do not necessarily represent the full scope of the disclosure, however, and reference is made therefore to the claims and herein for interpreting the scope of the disclosure.

[0025] FIG. 1 illustrates an example fail-operational steer-by-wire system. For example, the illustrated system may be a component of a vehicle, such as an off-highway vehicle (e.g., tractor, construction equipment, off-road recreational vehicle, etc.) comprising a hydraulic steering system 109. For example, steering system 109 may comprise a hydraulic steering axle operated via a hydraulic circuit. The direction and power could be separate signals or the direction signal be evident through multiple power signals, only some of which being powered at a time.

[0026] In some examples, a steer-by-wire system in a vehicle may include a generator 100 coupled to a mechanical steering input 113. For example, generator 100 may comprise an electric motor operable as a generator or a dedicated electric generator or other mechanical to electric conversion device. In some cases, generator 100 may by operated in a first manner during normal operation (e.g., when the normal steer-by-wire system is operational) and in a second manner during fail-over operation (e.g., when the normal steer-by-wire system is not operational). For instance, generator 100 may comprise a motor that provides haptic or force feedback to a user operating a mechanical steering input 113 during normal operation. For example, generator 100 may comprise a motor / generator that may be operated in a motor operational mode to provide opposing torque resistance to a steering wheel 113 to provide user steering feedback. In some examples, generator 100 may comprise a generator 100 that is unused during normal operation, such as a redundant generator. In various implementations, generator 100 may comprise any type of suitable electric generator (e.g.. having the ability to convert rotational shaft power to electrical power and, in some cases, vice-versa), such as a brushless direct current motor / generator (BLDC), a stepper motor / generator, an alternating current (AC) induction motor / generator, a brushed motor / generator, an axial flux motor, a linear electric motor / generator, a variable motor with gearbox, etc.

[0027] In the illustrated example, generator 100 may comprise a BLDC motor. For example, generator 100 may comprise an in-runner configuration BLDC motor comprising a rotor 101, a stator comprising windings 102, a motor control unit 103, and driver circuitry 104. When operated as a generator, a user may rotate the rotor 101 via a mechanical steering input 113. For instance, rotor 101 may be coupled to the shaft 114 of a steering wheel 113 to be turned when the user turns the steering wheel 1 13. As another example, rotor 101 may be coupled to a rack and pinion that converts linear motion of a mechanical steering input (e.g., pedals, joysticks, or levers) into rotary motion.

[0028] Generator 100 may generate an electrical signal 105 responsive to receiving directional input via a mechanical steering input 113. For example, a 3-phase generator 100may output an electrical signal 105 comprising three signal phases (e.g., one from each winding of stator 102). Electrical signal 105 may have an electrical signature corresponding to a direction. For example, electrical signal 105 may have a first phase signature corresponding to a first directional input and a second phase signature corresponding to a second directional input. For instance, in the illustrated example, when a user rotates rotor 101 in a clockwise direction, a signal may be generated by stator 102 having a phase signature corresponding to a sequence of windings: (A. B, C). Similarly, when the user rotates rotor in a counterclockwise direction, a signal may be generated phasing a phase signature corresponding to a sequence of windings (A, C, B). Of course, in other examples, other electrical signatures may correspond to different directional inputs. For instance, with a DC motor / generator or a 2 phase AC motor / generator. the electrical signature may comprise a first and second polarity (e.g., a positive voltage / polarity may correspond to a first direction and a negative voltage / polarity may correspond to a second direction. In other examples, a rotary position sensor 112 may optionally be present to aid in directional determination.

[0029] In some examples, a vehicle may further include a steering control circuit 108 coupled to the generator 100. The steering control circuit 108 may comprise circuitry to generate a steering control signal indicative of a direction based on the electrical signal 105. For example, steering control circuit 108 may comprise an analog-to-digital converter (ADC) and a processor (e.g., a microcontroller, digital signal processor, embedded processor, general purpose processor, etc.). As another example, steering control circuit 108 may comprise an ADC and D flip-flop (see, e.g., FIG. 3B). As a further example, steering control circuit 108 may comprise analog circuitry to detect a phase signature, such as a phase detector or phase comparator, or a sine-cosine resolver.

[0030] In some examples (a vehicle may further include converter 106 to convert electrical signal 105 into a power signal 107. For example, converter 106 may comprise convert an AC electrical signal 105 to a DC power signal 107. For instance, converter 106 may comprise a rectifier, such as a diode rectifier, ideal diode rectifier, transistor-based rectifier (e.g., a controlled MOSFET rectifier), buck / boost converter, a single-ended primary-inductor converter, a Cuk converter, etc. As another example, converter 106 may comprise an amplifier to amplify electrical signal 105 or electrical signal 107 to a sufficient power level to drive steering components (as described further below). In some examples, power signal 107 may be independent of the electrical signatures of the first and second electrical signals. For example, an electrical signal 105 of either type may be rectified to a positive DC voltage. In further examples, power signal 107 may have characteristics that correspond to the differentelectrical signatures. For instance, power signal 107 may be rectified to a positive voltage in response to a first directional input (e.g., turning a steering wheel 113 clockwise) and may be rectified to a negative voltage in response to a second directional input (e.g., turning the steering wheel 113 counterclockwise). In some such examples, the steering control signals and the power signal may be a combined electrical signal. For instance, steering control circuit 108 and converter 106 may be components of a common power / directional signal generating circuit. In other such examples, the power signal 107 and the steering control signals may be separate signals.

[0031] Optionally, if electrical signal 105 (e.g., the sinusoidal waveform) is able to provide a power output necessary for proper steering control, electrical signal 105 may sen e as power signal 107. For instance, responsive to manual turning the steering wheel 113 at typical rotational speeds, generator 100 may generate a proportional current, such as between 0- 1600mA, which may be sufficient to acuate a steering valve, such as a 24V (22ohm) solenoid. In particular, the power generated may be related to the change in axle position. For instance, in a sufficiently rapidly moving vehicle, steering wheel rotation may generate 1.5 A in less than a 45° rotation of the steering wheel. Of course, this is a particular example, implementations may have any suitable circuitry and / or mechanical componentry to provide suitable motor characteristics. For instance, shaft 114 may comprise a gear box to amplify the rotational speed of the rotor 101 with respect to the steering wheel 113.

[0032] In some examples, a vehicle may comprise a steering system 109 coupled to the steering control circuit 108. The steering system 109 may be configured to steer the vehicle in a first direction responsive to the first steering control signal and to steer the vehicle in a second direction responsive to the second steering control signal. For example, steering system 109 may comprise power circuitry 110 to receive power signal 107 and to use the power signal 107 to power a steering system component (e.g., a valve, pump, etc.). In some examples, steering system 109 may further include a direction selection circuit 111 coupled to the steering control circuit 108. The direction selection circuit 111 may be responsive to a steering control signal to control the application of the power signal by power circuitry 110 to a steering component. For example, direction selection circuit 111 may control the output of a double hydraulic pump or positioning of a three-way steering valve. Various example steering systems 109 are discussed further below.

[0033] In some examples, mechanical steering input 113 may comprise any mechanical device to provide directional input to steer a vehicle. While for sake of explanation mechanical steering input 113 may be described herein as a steering wheel, mechanical steering input 113is not limited to a steering wheel. For instance, mechanical steering input 113 may comprise a steering wheel, lever(s), joystick(s). pedals, etc. Accordingly, descriptions of rotating mechanical steering input 113 should be understood in this context and may include actuating other types of mechanical steering inputs 113 in their corresponding manners. In some examples, mechanical steering input 113 may comprise a human-machine interface (HMI) to enable an operator (e.g.. human driver) to steer the vehicle. In some examples, mechanical steering input 113 may comprise a mechanical steering input for a steering control device (e.g.. autonomous steering control system, remote operated control system, etc.). For example, mechanical steering input 113 may be actuated by an autonomous control system, such a control system guided via satellite navigation (e.g., GPS, GNSS), lidar, sonar, radar, etc. For instance, mechanical steering input 113 may comprise a steering wheel or other HMI with an added autonomous steering control system. As another example, mechanical steering input 113 may comprise a direct mechanical connection between an autonomous control unit and rotor 101.

[0034] FIG. 2 illustrates a second example fail-operational steer-by-wire system 200. For example, system 200 may comprise an implementation of a steer-by-wire system as described with respect to FIG. 1. System may comprise an operator powered generator 203 coupled to a steering system 205.

[0035] In this example, system 200 may include a mechanical steering input 201, such as a steering wheel (“steering wheel 201”). As illustrated, the shaft of steering wheel 201 may be coupled to a rotor of a generator 203, such as a BLDC motor. Generator 203 may be coupled to a converter circuit 204. For example, converter circuit 204 may comprise a rectifier to convert a 3-phase power signal output by generator 203 into a DC power signal. In some examples, steering wheel 201 and generator 203 may be coupled to a resistor, transformer, or other component. For instance, inclusion of a transformer may provide sufficient current generated in the motor to provide the back EMF needed to provide resistance for an operator to generate sufficient power at similar rotational speeds as a steering wheel 201 generator 203 arrangement lacking a transformer. For example, the transformer may support feedback torque to the operator based on the magnitude of electric power being generated and consumed.

[0036] In some examples, generator 203 may have different functionality in a normal operating state (e.g., when the normal steer-by-wire system is functioning normally). For instance, generator 203 may funchon as a motor to provide haptic feedback to an operator (e.g., to provide a torque against the direction of motion to provide a feeling similar to amechanical / hydraulic steering system). In various examples, generator 203 may comprise componentry operable during normal operation, such as torque sensors, position sensors, etc.

[0037] In some examples, system 200 may further comprise a power delivery circuit 202. For example, circuit 202 may comprise wires connected steering system 205. As another example, power deliver circuit 202 may comprise signal conditioning circuit components, such as amplifiers, transformers, etc. or protection circuit components such as diodes, fuses, varistors, etc.

[0038] In some examples, system 200 may comprise a steering system 205 to steer the vehicle response to steering control signals. For instance, steering system 205 may comprise direction selection circuitry 207, 208. For example, as illustrated, direction selection circuitry 207, 208 may comprise a dual ported arrangement of transistors as illustrated. As another example, a portion of direction selection circuitry 208 may comprise logic circuitry to steer the vehicle depending on a voltage state of a single direction selection line (e.g., a high voltage may indicate a first direction and a low voltage may indicate a second direction). For instance, circuitry 207 may comprise pMOS transistors while circuitry 208 may comprise nMOS transistors, such that portion 207 controls steering when a steering control signal is a high- voltage steering control signal and portion 208 controls steering when the steering control signal is a low-voltage steering control signal.

[0039] In some examples, steering system 205 may comprise a motive power source 206. For example, motive power source 206 may comprise a power source to actuate a steering actuator to steer the vehicle. For instance, motive power source 206 may comprise a motor (e.g., an electric motor) to drive an electric steering actuator, a motor to drive a hydraulic pump / motor steering actuator, a motor to drive a hydraulic pump coupled to a steering hydraulic cylinder (“steer cylinder”), dual solenoids to drive a directional solenoid valve coupled to a steer cylinder, etc. For example, motive power may be provided as a pulse- width- modulated (PWM) signal to solenoid-operated pilot valves to control the directional control valve. As another example, the directional control valve may comprise a direct driven spool control (i.e. stepper, brushed, BLDC) for the electrohydraulic control valve.

[0040] In some such examples, a directional solenoid valve may be powered itself by the power signal delivered via circuitry 202, a hydraulic pilot supply, a fail-operational electrical power supply, reduced power supply, etc.

[0041] In some examples, system 200 may further comprise fail-operational steering control circuitry 209. For example, circuitry 209 may comprise a steering control circuit or failure detection circuitry. In some examples, circuitry 209 may generate directional control signals(e.g., on separate corresponding signal lines, as different voltage states on a common signal line, etc.) as described herein. In some examples, circuitry 209 may comprise, suitable arrangements of electromechanical devices, diodes, comparators, transistors, other robust / simple circuitry to handle fail-over logic, directional logic and proportional power conversion and delivery without usage of complex electronics. Additionally, this may ease implementation as the failure modes may be more easy to assess with a system without complex electronics and software. In further examples, circuitry 209 may comprise digital logic, such as a processor and memory, a DSP, etc., analog logic, such as a circuit board, an application specific integrated circuit (ASIC). In some examples, fail-operational steering control circuitry 209 may comprise circuitry to perform further operations during normal operation. For instance, fail-operational circuitry 209 may provide diagnostic information or telemetry during normal operation. In some cases, circuitry 209 may be circuitry of the vehicle’s vehicle control unit (VCU), may be separated circuitry, or may be a combination thereof.

[0042] FIG. 3A illustrates example direction detection via phase comparison. Here, signals 303, 304, 305 may correspond to different phases of the electric signal received from a generator coupled to a mechanical steering input. For instance, signals 303. 304, 305 may comprise digital signals representative of the three phases (e.g., as output by an ADC or encoder coupled to the generator or due to the electrical characteristics of motor 203 on the phase power lines). Accordingly, the phase ordering of the digital signals may track the phase order of the signal created by the operator turning the generator. When a generator is turned clockwise 301, the sample sequence comprises (01 , 00, 10, 1 1) where a 1 indicates a high signal and a 0 indicates a low signal, the first digit corresponds to signal 303, and the second digit corresponds to signal 304). In comparison, when the generator is turned counterclockwise 302, the sample sequence comprises (11, 10, 00, 01). Accordingly, steering control circuitry may comprise logic to distinguish between these signal sequences to generate first and second steering control signals. Optionally, direction detection may be based on a subset of the phased signals. For instance, the signals of two of the three phase

[0043] FIG. 3B illustrates an example steering control circuit. In the illustrated example, steering control circuitry comprises a D-flip flop (DFF) 352 coupled to a first signal line 350 and a second signal line 351. For example, first and second signal lines 350, 351 may carry signals generated by an encoder or sin / cos output sensor resolved into logical outputs like an encoder. For example, sequences as described with respect to FIG. 3A may serve as codewords for an encoder to generate a first pair of signals generated responsive to a first detected sequence and to generate a second pair of signals responsive to a second detected sequence.For example, the codeword 01001011 might be decoded as a first signal pair where channel A350 is 90 degrees ahead of channel B 351 and the codeword 11100001 might be decodes as a second signal pair where channel A 350 is 90 degrees behind channel B 351. In the illustrated example, first signal line 350 is coupled to the data port d of DFF 352 and second signal line351 is coupled to the clock port. DFF 352 further comprises a data output port q coupled to a directional signal output 353. In this example. DFF 352 stores the state of signal line 350 (e.g., channel A) at the rising edge when the state of signal line 351 (e.g., channel B) enters a high voltage state. Accordingly, when channel A is 90 degrees ahead of channel B, DFF 352 stores a continuous 1 state and outputs a high voltage signal on output line 353. Similarly, when channel A is 90 degrees behind channel B, DFF 352 stores a continuous 0 state and outputs a low voltage signal on output line 353. As an example, a high voltage state might correspond to a clockwise steering wheel rotation and a low voltage state might correspond to a counterclockwise steering wheel rotation. In further examples, any suitable circuitry for phase detection may be employed, such as logic gate circuitry, microprocessor executed logic, etc.

[0044] FIG. 4 illustrates an example vehicle 400 including a fail-operational steer-by-wire system as described herein. For example, vehicle 400 may comprise an off-highway vehicle, such as a tractor, forklift, construction vehicle, etc. For example, vehicle 400 may implement any or all of the features described with respect to FIGS. 1-3. In some examples, the illustrated fail-operational steer-by-wire may be one of a redundant system of fail-operational system. For example, vehicle 400 may comprise an implementation of any other vehicle described herein, such as vehicle 500, 600 700, 800, 900 or any other vehicle described herein.

[0045] In some examples, vehicle 400 may include a mechanical steering input 401, such as a steering wheel, steering levers, steering pedals, etc. Vehicle 400 may further comprise a human-mechanical interface (HMI) 402. For example, interface 402 may comprise a direct coupling from the operator steering wheel 401 to a rotor of a generator 404. As another example, interface 402 may comprise a mechanical linkage coupling mechanical steering input 401 to generator 404 such as a spline, geartrain, pulley system, etc...

[0046] In some examples, vehicle 400 may further comprise a generator 404 coupled to mechanical steering input 401. As an example, vehicle 400 may comprise a steering wheel coupled to a BLDC motor / generator. As another example, vehicle 400 may comprise a steering levers or pedals coupled a linear generator or to a rack and pinion coupled to the shaft of a rotational generator. Generator 404 may generate electrical signals based on operator directional inputs. Such electric signals may comprise different electrical signatures such as phase order, voltage value, current value, inductance, back EMF, or polarities. For instance,in some examples, a first electrical signal (e.g., from turning a wheel in one direction) may comprise a first phase (jn and a second electrical signal (e.g., from turning the wheel in the other direction) may comprise a second phase 4>2. In some examples, electrical signals generated by generator 404 may have other parameters that may influence operation of the fail-operational steer-by-wire system. For instance, a user may rotate generator 404 at different rotational velocities co or apply different torques r to control the behaviour of a steering system. For example, the current of the electrical signal may vary based on the rate at which the operator actuates the mechanical steering input 401. For instance, a user may steer the vehicle to adjust a steering angle more quickly by turning a wheel faster.

[0047] In some examples, vehicle 400 may further comprise circuitry 406 coupled to generator 404. For example, circuitry 406 may comprise fail-over circuitry to control the initiation of back up steering operation. For instance, circuitry 406 may comprise inputs to receive data from other vehicle components, such as a sensor data or other telemetry. As another example, circuitry 406 may monitor electrical power provided by a vehicle electrical power supply 403 (e.g., a battery) or electrical power source 405 (e.g., an engine-driven alternator). Circuitry 406 may initiate a fail-over operation and transition to steering via the fail-operational steering system based on such received signals, such as, for example, a sensor signal indicating a failure of the normal steer-by-wire system or a loss / drop of power from source 405.

[0048] As an example, circuitry 406 may comprise a control unit (CU) and may include a computing system such as a processor (e.g., a controller) coupled to a memory (e.g., a flash storage). For example, circuitry 406 may comprise an electronic control unit (ECU), a vehicle control unit (VCU), steering control unit (SCU), a dedicated fail-operation control unit, etc. In some such examples, circuitry’ 406 may further comprise analog logic such as an ASIC or circuit board comprising logic components (e.g., comparators, transistor logic, diodes, etc.). In some examples, circuitry 406 may comprise a steering control circuit coupled to generator 402 to generate a first or second steering control signal responsive to a corresponding first or second electrical signature of electrical signal generated by generator 402.

[0049] In some examples, vehicle 400 may further comprise a hydraulic steering system. For instance, the steering system may comprise a hydraulic power supply 407 driven by a hydraulic poyver source (e.g., a pump). In this example, the vehicle 400 may comprise a hydraulic distribution circuit to provide hydraulic fluid to different vehicle components. For instance, vehicle 400 with a load sensing system may comprise a priority valve 412 that provides a prioritized fluid flow to a hydraulic supply 408 to the steering system.

[0050] In some examples, vehicle 400 may comprise a directional control valve 409 coupled to hydraulic source 408 and a hydraulic reservoir 410. For instance, in the illustrated example, directional control valve 409 may comprise a closed center three-way hydraulic valve. Directional control valve 409 may comprise work ports coupled to a steering actuator 413, 414. For instance, the illustrated example may comprise double acting hydraulic cylinders 413, 414 coupled to a steering axle 416 to control the orientation of wheels 411. For instance, in the illustrated example, when the valve is in the first position, hydraulic power may be delivered to extend cylinder 414 and retract cylinder 413. Similarly, when the valve is in the third position, hydraulic power may be delivered to retract cylinder 414 and extend cylinder 413 (e.g., the illustrated steering orientation). As illustrated, directional control valve 409 is coupled to generator 404 to power the valve 409 (e.g., via a rectifier, amplifier, etc. . . ). Further, directional control valve 409 may be coupled to circuitry 406 to receive a valve control signal. For instance, the valve control signal may comprise a steering control signal as described above. This example valve circuitry could be used for normal operation of machine wherein the operator moves the steering wheel 401, the motor / generator 404 position is sensed with either sensors or electrical characteristics and read by the control unit 406. Based on the wheel 401 position and velocity as well as steering axle feedback such as axle angle sensors 416, cylinder pressure sensors and other machine information (such as engine speed, wheel speed, seat position, etc ). The electronic control system 406 may give haptic / force feedback to the operator through controller the motor / generator 404 and control the wheel axles through controlling the electro-hydraulic control valve spool 409. In various examples, other aspects could also be controlled, such as the pump, priority devices, and other hydraulic and electrical systems.

[0051] As an example of fail-operational operation, circuitry 406 may detect a failure of a normal steer-by-wire system and initiate fail-over steer-by-wire operation. Detection of failure could be due to loss of electrical power, error in processor logic, error in sensors, etc. During the fail-over steering operation, an operator may actuate mechanical steering input 401 to produce a first directional input or a second directional input (e.g.. turning a wheel in one direction or another, actuating one lever vs another, etc.). The directional input may drive generator 404 via HMI 401 to generate a first electrical signal having a first electrical signature responsive to a first directional input and to generate a second electrical signal having a second electrical signature responsive to the second directional input. Generator 404 may generate a power signal to operate valve 409. Here, circuitry 406 may generate a first steering control signal or a second steering control signal responsive to the first or second electrical signature.Circuitry 409 may transmit a steering control signal to control the position of directional control valve 409 using the power signal. Operation of directional control valve 409 may then actuate the hydraulic steering axle in one direction or the other based on the steering control signal. Accordingly, as illustrated, an operator may generate power sufficient to actuate a hydraulic steering system and the manner of operation (e.g., direction of rotation) may control the direction or velocity of the steering actuation. This allows steering control to be maintained even when the vehicle 400 has experienced a failure detected by circuitry 406 (e.g.. a loss of machine electrical power or another failure).

[0052] FIG. 5 illustrates another example vehicle 500 having a fail-operational steer-by-wire steering system. Vehicle 500 may include any or all features described with respect to FIGS. 1-3. In some cases, vehicle 500 may comprise an alternative implementation compared to vehicles 400, 600, 700, 900, or other vehicle described herein. As another example, vehicle 500 may comprise an implementation of a vehicle 400, 600, 700, 900 or any other vehicle described herein comprising a further (e.g., redundant) back up steer-by-wire steering system. In some examples the valve 507 or the pump 516 can be used either as main or fail-operational steering control. As illustrated, the valve 507 may be controlled by the electronic control unit in normal operation, but in fail-operational the bi-directional pump may be controlled by electrical power generated from source 502. Alternatively, the power or direction signal generated from 502 can be amplified electrically and sent to the pump 516 if more power is required than what the generator 502 can provide to steer the machine.

[0053] As illustrated, vehicle 500 may comprise a mechanical steering input 501 , a generator and circuitry7502, an electrical power source / supply 504, a hydraulic power supply 505, a priority valve 512, a hydraulic supply line 506, directional control valve 507, and a steering axle comprising steering actuators 517, 518. In some examples, these elements may be implemented or operated as described with respect to mechanical steering input 401, generator 404 and circuitry 406, hydraulic power supply 407, priority valve 412, hydraulic supply line 408, directional control valve 409, and steering axle 416 including steering actuators 413, 414 as described with respect to FIG. 4.

[0054] In some examples, vehicle 500 may include a steering system comprising an electrohydraulic pump 514 (“e-pump 514”) coupled to the hydraulic power delivery system 513, 515 (e.g., tubes, hoses, leakage protection components (e.g., pilot-operated (PO) check valves), makeup flow circuits, etc. For instance, e-pump 514 may comprise a tandem or bidirectional e-pump coupled between the work ports of the directional control valve 507 or coupled between work ports 519, 520 of the steering actuators 518, 517. The inclusion of thee-pump 514 allows for steering operation to be maintained even where a primary hydraulic component (e.g.. pump 505. priority valve 512) has ceased functioning, or is functioning at reduced capacity (e.g., due to leaks in the system).

[0055] In some examples, fail-operational control circuitry (e.g., illustrated as cohoused with motor / generator 502) may comprise circuitry7to initiate steering control via e-pump 514. For example, fail-operational control circuitry may receive sensor data from the hydraulic power delivery system 505, 503, 506, 507. 509 to detect a steering failure. For example, fail- operational control circuitry^ may be coupled to steering valve sensors 511, 510 to detect a failure of the directional control valve 507 (e.g., a failure to actuate). As another example, fail- operational control circuitry may be coupled to a pressure sensor 503 to detect a failure of the priority valve 512 or pump 505 (e.g., loss of normal operating pressure). Fail-operational control circuitry may be configured to initiate fail-over steering e-pump 514 based on any suitable failure indicator. For instance, fail-operational control circuitry may initiate fail-over steering responsive to receiving sensor data indicating a failure, or failure to receive data from a sensor or other component (e.g., failure to response to a polling signal or failure to deliver a heartbeat signal), or other parameters indicative of a steering system failure.

[0056] In some examples, steering control circuitry of generator / circuitry 502 may be coupled to e-pump 514 via electrical lines 508 to transmit steering control signals. Responsive to a first steering control signal (e.g., a signal on a dedicated signal line or voltage encoded signal on a shared signal line), e-pump 514 may pump in a first direction to pressurize a first steering hydraulic delivery circuit 513 and depressurize a second hydraulic delivery circuit 515. Accordingly, in the first direction, hydraulic cylinder 517 is extended and hydraulic cylinder 518 is retracted and vehicle 500 is steered to the right (where FIG. 6 provides a top-down viewpoint). For instance, the first steering control signal may be generated responsive to an operator actuating mechanical steering input 501 to steer the vehicle rightwards (e.g., a clockwise rotation of a steering wheel). Similarly, responsive to a second steering control signal, e-pump 514 may pressurize supply side 515 and actuate side 515 to extend cylinder 518 and retract cylinder 517 to steer the vehicle leftwards. For instance, the second steering control signal may be generated responsive to the operator actuating mechanical steering input 501 to steer the vehicle leftwards (e.g., counterclockwise rotation of a steering wheel).

[0057] In some examples, generator / circuitry7502 may further provide a power signal via line(s) 508 to power the pump (in addition to controlling the pump direction). For instance, generator / circuitry 502 may transmit 3-phase current generated via the operator actuating input 501 to an AC e-pump 514. As another example, generator / circuitry 502 may comprise arectifier or DC-output generator to transmit a DC current to a DC e-pump 514. In further examples, e-pump 514 may be coupled to and driven by a vehicle electrical power supply 504 (e.g., battery or alternator). For example, e-pump 514 may be independently coupled to electrical power supply 504. As another example, a power signal provided by generator / circuitry 502 may be amplified via electrical power source 504 which then drives e- pump 514.

[0058] FIG. 6 illustrates another example vehicle 600 having a fail-operational steer-by-wire steering system, which may implement any or all of the features described with respect to FIGS. 1-3. Vehicle 600 may comprise an alternative implementation compared to vehicles 400, 500, 600, 700. 800, 900, or other vehicles described herein. As another example, vehicle 600 may comprise a redundant fail-operational system to a system as illustrated with respect to vehicles 400, 500, 700, 800, 900, or other vehicle described herein.

[0059] As illustrated, vehicle 600 may comprise a mechanical steering input 601, a generator and circuitry 603, an electrical power source / supply 602, a hydraulic power supply 605, a hydraulic supply line 606, directional control valve 607, and a steering axle comprising steering actuators 609, 611. In some examples, these elements may be implemented or operated as described with respect to mechanical steering input 401 / 501, generator 404 and circuitry 406, generator / circuitry 502, hydraulic power supply 407 / 505, priority' valve 412 / 607, hydraulic supply line 408 / 606, directional control valve 506 / 409, and steering axle 416 including steering actuators 413 / 517, 414 / 518 as described with respect to FIGS. 4, 6. respectively.

[0060] In this example, the vehicle steering system may lack a priority valve to prioritize hydraulic steering power in case of reduced functionality7of hydraulic power supply 605Here, vehicle 600 may further comprise a secondary hydraulic power supply 608. For instance, secondary hydraulic power supply 608 may be coupled to an axle 612 or other drive train component (e.g., a wheel-contacting ground driven pump). In some examples, secondary hydraulic power supply7608 may be engaged responsive to a control signal from a fail- operational control circuit (e.g., included in generator / circuitry' 603, a VCU, etc.) responsive to pressure data from pressure sensor 604 indicating pressure loss / reduction.

[0061] FIG. 7 illustrates another example vehicle 700 having a fail-operational steer-by-wire steering system. For example, vehicle 700 may comprise an alternative implementation compared to vehicles 400, 500, 600. As another example, vehicle 700 may comprise a redundant fail-operational system to a system as illustrated with respect to vehicles 400, 500, 600. Accordingly, as indicated, vehicles implementing the described technology may have a variety of levels of redundancy operated / controlled by vehicle operator-generated power.

[0062] In the illustrated example, vehicle 700 may comprise a mechanical steering input 701, a generator and circuitry 703, an electrical power source / supply 702, e-pump 707, and a steering axle comprising steering actuator(s) 704, 705. In some examples, these elements may be implemented or operated as described with respect to mechanical steering input 401 / 501 / 601, generator 404 and circuitry 406, generator / circuitry 502 / 603, e-pump 514 / 610, and steering axle 416 including steering actuators 413 / 517 / 609, 414 / 518 / 611 as described with respect to FIGS. 4. 5, 6 (as applicable).

[0063] In this example, hydraulic source components, such as a hydraulic power supply, a hydraulic supply line, or a directional control valve are not illustrated. For instance, vehicle 700 may comprise a closed hydraulic steering system. For example, vehicle 700 may comprise an e-pump 706 that is driven by vehicle electrical power provided by supply 702 during normal operation. As another example, the illustration may represent a reservoir-based system under loss of hydraulic power or failure of a directional control valve.

[0064] In this example, vehicle 700 may further include a secondary electric power source 707, such as a ground drive, auxiliary engine, backup battery, etc. Continuing the example, fail-operational control circuitry may engage an operator-driven fail-operational steering system responsive to an electrical failure interfering with normal steer-by-wire operation (e.g., electrical power supply 702 failing, a VCU failure, or other electrical fault). For example, fail- operational control circuitry may engage secondary power source 707 to drive e-pump 707 under directional control signals generated by fail-operational control circuitry (e.g., generator / circuit 703). As another example, fail-operational control circuitry may drive e- pump via operator-generated electricity7(e.g., to supplement or provide redundancy for secondary' power supply 707). In this way, the vehicle can generate increased electrical output to power the motor for more responsive steering in the event and electrical failure.

[0065] While the preceding examples are generally described with respect to a hydraulic steering system, the described technology may be implemented in vehicles having any ty pe of steering system. For instance, a vehicle may comprise an electrically actuated steering (“e- steenng") system. For example, steering actuators in such a system may comprise all-electric steering actuators (e-actuator). In such systems, operator-generated power may be supplied to the e-steering system as a backup to the normally powered steer-by-wire system. For example, operator-generated directional control signals may be transmitted to an e-actuator selector to control which e-actuator is actuated by a power signal provided by the vehicle’s electric power supply, ground drive backup power supply, etc. Accordingly, the described technology may support e-actuated steering systems without requiring a secondary electrical battery or system(e.g., in small machines or other equipment where an operator actuating a mechanical input provides sufficient power to drive the e-steering system). As an example, FIG. 8 illustrates an example vehicle 800 comprising a fail-operational e-steering in a system architecture similar to that of vehicle 700. In the illustrated example, vehicle 800 may comprise a mechanical steering input 801, a generator and circuitry 803, and an electrical power source / supply 802. Accordingly, vehicle 800 may include any feature as described with respect to FIGS. 1-3, other than features that are specific to hydraulic steering. In some examples, these elements may be implemented or operated as described with respect to mechanical steering input 401 / 501 / 601 / 701, generator 404 and circuitry 406, and generate r / circuitry 502 / 603 / 703. Of course, the illustrated e-system does not preclude hydraulic steering systems and the illustrated e-steering system may be a redundant system to a hydraulic steering system. Further, in some examples, vehicle 800 may comprise an implementation of another vehicle described herein, such as vehicle 400, 500, 600, 700, 900.

[0066] Vehicle 800 may include an e-steering system 806 coupled to electronic actuator(s) 805, 804 for controlling the steering axle. For example, e-steering system 806 and actuators 805, 804 may comprise a rack and pinion steering system driven by an electric motor. As discussed above, in some examples, power from generator / circuitry 803 may provide fail- operational power generated by mechanical input 801. As a further example, vehicle 800 may comprise an electrical power source 802, which may be used by generator / circuitry 803 to power e-steering system 806 based on control signal generated by mechanical input 801. As another example, vehicle 800 may optionally include a secondary electric power source 807, such as a ground drive, auxiliary engine, backup battery, etc., which may power e-steering system 806 based on control signals generated by mechanical input 801.

[0067] FIG. 9 illustrates an example vehicle 900 including fail-operational steering control circuitry comprising a microprocessor 906 and a secondary steering control signal generator circuit 907. For instance, vehicle 900 may comprise any vehicle implemented the described technology, such as the examples described above.

[0068] In this example, a vehicle steering system may comprise a processor-based logic subsystem 906. For example, subsystem 906 may comprise a VCU, a dedicated steering controller, etc. As an example, subsystem 906 may comprise a microprocessor, memory / storage 904, ancillary circuitry, a circuit board, etc. (‘‘microprocessor 906”). For example, memory / storage 904 may comprise a flash memorv. a read-only -memory, randomaccess memory (RAM), or other non-transitory computer readable medium. Accordingly, microprocessor 906 may execute code stored on a non-transitory computer readable mediumto perform various aspects of the above-described operations. For example, microprocessor906 may be coupled to a steering system 917 via signal line(s) 910 to transmit normal operation / main steering control signals.

[0069] In some examples, microprocessor 906 may store instructions to implement aspects of a fail-operational steering system, such as a fault detection or failover initiation. For instance, microprocessor 906 may store instructions to diagnose a hydraulic-related failure in a hydraulic steering system (e.g.. loss of pressure, valve failure, etc.). Microprocessor 906 may be coupled to a steering control circuit 907 to transmit a fail-over steering initiation signal 903 responsive to a determined fault.

[0070] In some examples, steering control circuit 907 may be coupled to a motor / generator 901 coupled to a mechanical steering input. For example, steering control circuit 907 may be coupled to signal lines 902 carrying a three-phase electrical signal output by motor / generator 901. For instance, the three-phase electrical signal may comprise a signal having a first phase signature responsive to a first directional input to motor / generator 901 and may comprise a signal having a second phase signature responsive to a second directional input.

[0071] In some examples, steering control circuit 907 may comprise circuitry to receive the first electrical signal and the second electrical signal, to generate a first steering control signal responsive to the first electrical signature, and to generate a second steering control signal responsive to the second electrical signature. For instance, steering control circuit 907 may comprise a phase signature determination circuit as described above. Steering control circuit907 may be coupled to steering system 912 to transmit the first / second steering control circuits (e.g., secondary steering signals).

[0072] In some examples, microprocessor 906 may transmit secondary / tertiaiy steering control signals 911. For instance, steering control circuit 907 may include a communication interface 905 to transmit a passthrough directional control signal via microprocessor 906 (as opposed to directly via signal lines 909). For example, the steering control system may use the microprocessor 906 to transmit the fail-over steering signal 911 when the microprocessor 906 is operational. For instance, this may support microprocessor 906 logging the failure, controlling other fail-operational systems, diagnosing a cause of the failure, etc.

[0073] In other cases, such as an electrical or controller failure, steering control circuit 907 may identify the failure and become fail-operational without microprocessor interaction. This could be identified through watchdog circuitry not being handled in proper timing, or no signal from the controller at all. In some such examples, steering control circuit 907 may transmit a steering control signal 909 in the event of a microprocessor 906 failure. For example, steeringcontrol circuit 907 may be coupled to microprocessor 906 via signal line 905 carrying polling / watchdog / heartbeat or other “alive” periodic signal to support steering control circuit 907 detecting a microprocessor failure.

[0074] In some examples, steering control circuit 907 may provide various other functionality. For instance, steering control circuit 907 may be coupled to microprocessor 906 via signal line 908 to provide telemetry signals or diagnostic signals, such as motor generator rotational velocity, rotational direction, power output, operational status, etc.

[0075] Of course, the illustrated arrangement is not necessarily indicative of arrangement of circuitry or components. For instance, motor / generator 901, microprocessor 906, and circuit 907 could be co-housed as a single unit, or could be distributed across any number of units.

[0076] The description of the different advantageous embodiments has been presented for purposes of illustration and description and is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different advantageous embodiments may provide different advantages as compared to other advantageous embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary7skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMSWhat is claimed is:

1. A steering system comprising: an actuator to adjust a steering angle of the steering system; a primary electrical power source to provide a first flow of electrical power; a mechanical to electrical conversion device to convert a mechanical steering input into a second flow of electrical power; and circuitry to switch operation of the steering system based on detection of a fault, the circuitry switching between: a normal mode in which the first flow of electrical power from the primary electrical power source causes the actuator to adjust the steering angle, and a fail-operational mode in which the second flow of electric power from the mechanical to electrical conversion device causes the actuator to adjust the steering angle.

2. The steering system of claim 1, wherein the mechanical to electrical conversion device comprises a permanent magnet motor / generator to convert rotary power into electrical power.

3. The steering system of claim 2, wherein the permanent magnet motor / generator comprises a brushless DC electric (BLDC) motor / generator.

4. The steering system of claim 3, wherein, in the normal mode, the BLDC motor / generator provides active torque feedback.

5. The steering system of claim 1, further comprising a rectifier circuit coupled to the mechanical to electrical conversion device to receive a 3-phase AC signal from the mechanical to electrical conversion device and to output power to cause the actuator to adjust the steering angle.

6. The steering system of claim 5, wherein the rectifier circuit comprises a buck / boost converter, a single-ended primary-inductor converter, or a Cuk converter.

7. The steering system of claim 1, further comprising a steering control circuit coupled to the mechanical to electrical conversion device to determine a direction of the steering system based on a phase order of a 3-phase AC signal received from the mechanical to electrical conversion device.

8. The steering system of claim 1 , wherein the mechanical to electrical conversion device is coupled to a translational to rotational device to convert translational power to rotary power for the mechanical to electrical conversion device.

9. The steering system of claim 1, further comprising a direction sensor coupled to a human mechanical interface to determine a steering direction of the human mechanical interface.

10. The steering system of claim 9, further comprising a direction detection circuit to, responsive to a failure of the direction sensor to determine the steering direction, determine a direction of the human mechanical interface based on a phase order of a 3-phase AC signal received from the mechanical to electrical conversion device.

11. The steering system of claim 10, further comprising circuitry to power the direction sensor using the second flow of electrical power.

12. The steering system of claim 1. further comprising a secondary’ electrical power source to amplify the second flow of electrical power to adjust the steering angle.

13. The steering system of claim 1, wherein, in the second mode of operation, the second flow of electric power from the mechanical to electrical conversion device powers adjustment of the steering angle responsive to a failure of the primary electrical power source or a failure of a primary controller.

14. The steering system of claim 13, further comprising logic circuitry to detect the failure of the primary' electrical pow er source.

15. The steering system of claim 13, further comprising logic circuitry to detect the failure of the primary’ controller.

16. The steering system of claim 13, further comprising secondary' power circuitry to supply a steering system or braking system component responsive to the failure of the primary electrical supply or the failure of the primary controller.

17. The steering system of claim 1, further comprising a first hydraulic pump to supply a first flow of hydraulic fluid to operate the actuator.

18. The steering system of claim 17, wherein the first hydraulic pump is driven by an electric motor that receives the first flow of electrical power in the normal mode and receives the second flow of electrical power in the fail-operational mode.

19. The steering system of claim 17, further comprising a directional control valve between the first hydraulic pump and the actuator to control a direction of change in the steering angle, wherein the first flow of electrical power is provided to the directional control valve in the normal mode, wherein the second flow of electrical power is provided to the directional control valve in the fail-operational mode, and wherein the circuitry comprises an electrical circuit to control the actuator based on a change in a direction of the mechanical steering input, and to determine the direction of the mechanical steering input based on the second flow of electrical power in at least one of the normal mode and the fail-operational mode.

20. The steering system of claim 19, wherein the second flow of electrical power is used to generate a pulse-width-modulated (PWM) signal to operate solenoid-operated pilot valves to control the directional control valve.

21. The steering system of claim 19, wherein the electrical circuit comprises a microprocessor.

22. The steering system of claim 1, further comprising an electric steering actuator controlled by the second flow of power in the fail-operational mode.

23. The steering system of claim 1, further comprising an electric motor driven hydraulic steering control unit powered by the second flow of power in the fail-operational mode.

24. The steering system of claim 1 , further comprising: a microprocessor to generate steering control signals; and a watchdog circuit to monitor an operational status of the microprocessor.

25. The steering system of claim 24, wherein the watchdog circuit is coupled to the circuitry to trigger the fail-operational mode of operation responsive to detecting a failure of the microprocessor.

26. The steering system of claim 1, wherein the circuitry comprises a microprocessor.

27. A vehicle, comprising: a mechanical steering input to receive a first directional input and a second directional input; a mechanical to electrical conversion device coupled to the mechanical steering input to generate a first electrical signal having a first electrical signature responsive to the first directional input and to generate a second electrical signal having a second electrical signature responsive to the second directional input; a steering control circuit coupled to the mechanical to electrical conversion device to receive the first electrical signal and the second electrical signal, the steering control circuit to generate a first steering control signal responsive to the first electrical signature and to generate a second steering control signal responsive to the second electrical signature; and a steering system coupled to the steering control circuit to steer the vehicle in a first direction responsive to the first steering control signal and to steer the vehicle in a second direction responsive to the second steering control signal.

28. The vehicle of claim 27, wherein: the first electrical signature comprises a first phase signature; and the second electrical signature comprises a second phase signature.

29. The vehicle of claim 27, wherein: the first electrical signature comprises a first signal polarity: and the second electrical signature comprises a second signal polarity.

30. The vehicle of claim 27, further comprising: a converter coupled to the mechanical to electrical conversion device to convert the first electrical signal and the second electrical signal to produce a power signal, and a direction selection circuit coupled to the steering control circuit and the steering system to control transmission of the power signal to the steering system to steer the vehicle in the first direction based on the first steering control signal and to steer the vehicle in the second direction based on the second steering control signal.

31. The vehicle of claim 27, wherein the steering system comprises a hydraulic pump.

32. The vehicle of claim 31 , wherein the steering system further comprises an electric motor coupled to the hydraulic pump.

33. The vehicle of claim 27, wherein the steering system further comprises an electrically actuated steering system.

34. The vehicle of claim 27, wherein the steering system further comprises a hydraulic directional control valve coupled to the mechanical to electrical conversion device.

35. The vehicle of claim 27, wherein the steering system comprises a solenoid and a directional control valve.

36. The vehicle of claim 27, wherein the mechanical steering input comprises a steering wheel to be turned by an operator in a first rotational direction to provide the first directional input and to be turned by the operator in a second rotational direction to provide the second directional input.

37. The vehicle of claim 36, wherein the mechanical to electrical conversion device is coupled to the steering wheel to be driven by the operator turning the steering wheel.

38. A steering system comprising: an actuator configured to adjust a steering angle; a primary power source to supply a first flow of power to operate the actuator; a secondary power source to supply a second flow of power to operate the actuator; a mechanical steering input configured to receive a steering input from an operator; a mechanical to electrical conversion device coupled to the mechanical steering input to generate an electrical signal based on the steering input; and circuitry configured to switch operation of the steering system between: a first mode in which the circuitry' controls a flow of power from the primary power source to operate the actuator based on the steering input, and a second mode in which power is supplied from the secondary power source to operate the actuator to adjust the steering angle based on the electrical signal.

39. The steering system of claim 38, wherein the primary power source comprises an electrical power source and the electrical signal is a power signal.

40. The steering system of claim 39, wherein the secondary power source comprises an electric motor or a generator configured to couple to an axle to generate electrical power based on rotation of the axle.

41. The steering system of claim 40, further comprising an amplifier coupled to the secondary' power source and the mechanical to electrical conversion device to amplify the electrical signal to generate the power signal.

42. A steering system comprising: an actuator to adjust a steering angle of the steering system; a primary electrical power source to provide a first flow of electrical power; a mechanical to electrical conversion device to convert a mechanical steering input into a second flow of electrical power; and circuitry to detect a fault the steering system and based on detection of the fault in the steering system to switch operation of the steering system between: a normal mode in which the first flow of electrical power from the primary electrical power source causes the actuator to adjust the steering angle, and a fail-operational mode in which the second flow of electric power from the mechanical to electrical conversion device causes the actuator to adjust the steering angle.

43. The steering system of claim 0, further comprising a first hydraulic pump to supply a first flow of hydraulic fluid to operate the actuator.

44. The steering system of claim 43, wherein the first hydraulic pump is driven by an electric motor that receives the first flow of electrical power in the normal mode and receives the second flow of electrical power in the fail-operational mode.

45. The steering system of claim 44, further comprising an auxiliary power supply that supplies a third flow of electrical power to the electric motor in the fail-operational mode.

46. The steering system of claim 43, further comprising a directional control valve between the first hydraulic pump and the actuator to control a direction of change in the steering angle, wherein the first flow of electrical power is provided to the directional control valve, and wherein the circuitry determines the direction of change in the steering angle based on the second flow of electrical power in both the normal mode and the fail-operational mode.

47. The steering system of claim 46, wherein the second flow of electrical power is provided to the directional control valve.

48. The steering system of claim 46, further comprising a second hydraulic pump to provide a second flow of hydraulic fluid to the actuator, wherein the second hydraulic pump is driven by an electric motor that receives the second flow of electrical power.

49. The steering system of claim 48, wherein the second hydraulic pump is between the directional control valve and the actuator.

50. The steering system of claim48, further comprising a third hydraulic pump configured to provide a third flow of hydraulic fluid to the actuator.

51. The steering system of claim 50, wherein the third hydraulic pump is coupled between the first hydraulic pump and the directional control valve.

52. The steering system of claim 50, wherein the third hydraulic pump is operated by an axle of the steering system.

53. The steering system of claim 0, wherein the circuitry comprises a fail- operational circuit to detect at least one of a mechanical fault and an electrical fault in the steering system.

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