FAULT-TOLERANT SYSTEM

Abstract: A fault tolerant system (5) for a vehicle comprises an input node for receiving an input signal and at least two nodes coupled to the input node. Each node has a control means (10, 20, 30, or 40) arranged for processing the input signal to provide a second signal for controlling at least one actuator (15, 25, 35, 45), and to provide a plurality of third signals to the at least one other control means (10, 20, 30, or 40); the third signals are the expected second signal results of the at least one other control means. Each control means (10, 20, 30, or 40) is arranged to compare the second signal with the third signals received from the at least one other control means such that errors detected between the second and third signals indicate faults in the at least one control means.

Description: FAULT-TOLERANT SYSTEM Field of the Invention This invention relates to fault-toierant systems sucn as fault-tolerant suspension systems, fault-tolerant electronic comoustion cimαer e control systems and to fault-tolerant steeπnε svstems. BacKsround of the Invention In recent years, automobile manufacturers have sought to replace many expensiv e mechanical components with electronic components. Future automotive designs contemplate the removal of even more mechanical components, particularly m respect of control linkages to the engine, wheels, etc... replacing them with " by-wire " technology, pamally derived from the 'fly-by- wire ' technology associated with the aircraft industry. For example, the hydraulic or mechanical suspension system or the steering system of an automobile may be replaced by a microprocessor controlled system, having a sensors or switches which, upon actuation by the driver or due to certain road conditions, transmits electronic signals to actuators located in proximity to the wheels. In a suspension system, the actuators apply damping to the vehicle suspension in dependence on the electronic signals. In a steering system, the actuators are arranged to turn the wheels of the vehicle in order to change the direction m which the vehicle is travelling in dependence on the electronic signals. Similarly, the mechanical or mechanical with hydraulic assistance cylinder valve system of an automobile may be replaced by a microprocessor controlled svstem. having sensors or switches which, upon actuation by the dπver or combustion conditions, transmit electronic signals to valve actuators located in proximity to the combustion cylinders. The vah e actuators are arranged to position the combustion cvhnder intake and exnaust \ aives m order to change the comoustion conditions within the cylinders in dependence UΌOΠ the electronic signals. In highh depenαabie applications, sucn as the suspension, steeπng and electronic \ alve control svstems described above, me stem must De fault-tolerant, such that if a fault should occur, at least some functionality of the system w ill continue Known arrangements to provide fault-tolerance include redundant systems having two or more microprocessors which operate independently of each other and cross-check each other to detect faults. A problem with this arrangement is that the larger the number of processors, the more cost is added to the system, and the fewer the number of processors, the greater the chances of all processors m the system developing a fault. This invention seeks to provide a fault-toierant suspension system nich mitigates the aDove mentioned disadvantages. Summarv of the Invention According to the present invention there is provided a fault tolerant system for a \ ehicle. compnsmg: an input node for receiving an input signal; and at least two nodes coupled to the input node, each node being arranged to control at least one actuator, each node having control means arranged for processing the input signal to provide a second signal for controlling the at least one actuator, and to provide a plurality of third signals to the at least one other control means, the third signals being expected second signal results of the at least one other control means, wherein each control means is arranged to compare the second signal with the third signals received from the at least one other control means such that errors detected between the second and third signals indicate faults in the at least two control means. Preferably upon detection of a fault, each control means uses a voting scheme to determine which of the second and third signals is to be used as a fourth signal to control each of the actuators. Each control means is aiso preferably arranged to transmit the fourth signal to the at least one other control means, in order to verify whether the \ oting scheme has been used correct!} The at least two nodes are preferably distributed in mutually remote locations in e venicle. Preferably the input signal is adapted such mat it is transmitted to me a: .east two nodes in a synchronous manner. The input signal is preferably re-transmitted by each of the control means, for fuπner fault detection. Preferably for a fault-tolerant suspension system, the system composes three nodes and the actuators are suspension actuators, each node being arranged to control one of three suspension actuators. Preferably for a fault-tolerant steeπng system, the s\ stem composes an user operated input unit arranged to provide me input signal m response to operation thereof and the actuators are steeπng actuators Preferably for a fault tolerant electronic valve control svstem. the system composes three nodes and wherein the actuators are valve actuators, each node being aoanged to control one of three valve actuators. Preferably, the nodes are distobuted locallv with respect to each other and proximate to the cylinders in the vehicle In this way a fault-tolerant system is provided which is cost effective, with improved fault-tolerance and enhanced fault-detection. Bπef Descπption of the Drawings A fault-tolerant suspension system and a fault- tolerant steering system in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: FIG. 1 shows a block schematic diagram of a fault-tolerant suspension system in accordance with the present invention: FIG. 2 shows a block schematic diagram of a fault-tolerant steeπng sv stem in accordance with the present invention: and FIG. 3 shows a block schematic diagram of a fault-tolerant electronic v alve control system in accordance with the present invention Detailed Descπption Referπng to FIG 1. there is sho n a fault-tolerant suspension sv stem 5 for a v ehicle ( not show n ) in accordance with a first embodiment of the present inv ention. including first, second, third, and fourth suspension nodes having electronic control units l EC s ) 10. 20. 30 and 40. which are distobuted in mutually remote locations the vehicle Each of the first, second, third, and fourth ECUs 10. 20. 30 and 40. are coupled to associated first. second, third and fourth suspension actuators 15. 25. 34. 45 respectively The first, second, third, and fourth ECUs 10, 20, 30 and 40 respectively are also each coupled to first and second buses 7 and 8 respectively An input node provides an input signal to the first 10. second 20. third 30 and fourth 40 ECUs via the first 7 and second 8 buses Preferably, there are at least two input nodes, the first input node being coupled to an user operated input unit 50 and a second input node being coupled to a sensor Each ot the ECUs 10. 20. 30 and 40 receives an input signal rrom the input unit 50 ana or an input signal from the sensor In the embodiment show n in FIG .. there are five input nodes the first input node being coupled to the input unit 50. and second, third, rouπh and fifth input nodes being coupled to sensors 65. 70, 80 and 90 respectively Each of the ECUs 10. 20. 30 and 40 receives an input signal from the input unit 50 and or an input signal from one or all of the sensors o5 " 0. 80. and 90 The first and second buses ~ and 8 respectively are substantially identical and are poth arranged to provide synchronous signals according to a Time Di ision Multiple Access scheme (TDMA) or similar scheme High level functions of current suspension systems may be integrated into the system 5 via a (high level) ECU 60 coupled to the buses 7 and 8, or by a gateway to an ECU (not shown). The input unit 50. which is preferably a switch or switches, is arranged to provide user input signals to the system For example, the user input signals may indicate whether a sports or a more comfortable suspension setting is required The sensors 65. 7 0. 80 and 90. which in the preferred embodiment are shown as oeing coupled to the first 7 and second S buses, are aoanged to detect v aoations in the motion ot the vehicle with respect to it s position and attitude to the suπace upon hicn its is travelling The sensors 65. Y 80 and 90 provide signals to the ECUs 10. 20. 30 and 40 in dependence on the lniormation detected bv the sensors The sensors 65. " 0 iϋ and 90 mav be arranged to pre-process tne mtormation supplied to the EC _> Eacn of the first, second, third and fouπh ECUs 1 . 20 30. 40. can operate independently from the other ECL s if required, and are able to pro ide a processed result signal to the associated suspension actuator 15. 25. 35 or 45 m response to the signals received from the input unit 50 and/or sensors 65, 70, 80 and 90 In this way a basic suspension function is achieved, which is the minimum required for safe operation, not necessarily including hisher lev el functions such as vehicle stability mana g ement The provision of first and second buses 7 and 8 provides fault-tolerance in the case of a problem occurring therein. In addition, each of the first, second, third, and fourth 1 . 20. 30. 40. ECUs. performs a similar algoothm using the same signals received from the input unit 5υ and or the sensors 65. " 0. 80 and 90. and provides the received signals ana the result signals to the other ECU ' s. In this way each of the first, second, third, and fouπh ECUs 10. 20. 30. 40. can detect incorrect operation by compaong its received signals and result signals with those received signals and result signals received from the other ECUs As four ECUs are available to check the same signals, it is possible to not only detect that there is a problem somewhere m the system 5. but also to identify the faulty ECU. A faulty ECU can therefore be identified, either by itself, or by the majooty of the ECUs in the system 5 via a voting procedure, whereby the ECU having the most different results compared to the other ECUs is considered to be faulty. After a fault has been identified, appropriate action can be taken, such as logging the fault, running diagnostics, or resetting or disabling the node. If an ECU is disabled due to a fault, the system 5 can be arranged such that the mam suspension function will be re- distributed across the operating ECUs. As each ECU checks its operation against the other ECUs. faults can be detected that may be undetectable by using a simpler self-test type of checking in isolation. For example, an ECU may exhibit a fault where it decodes the received signals from the input unit 50 incorrectly, but the decoded value is still withm the allowed range The ECU would pass a self-test, and act on the faulty data if no other tests were performed, but with the described checking against other ECUs. the incorrect data would be detected. As each ECU regularly re-transmits their receiv ed signals, the sv stem 5 is able to survive faults that would otherwise cause it to be partialh disabled. For example, if the first ECU 10 cannot access the signals from the input unit 5ϋ and or sensors 65. " 0, 80 and 90 directly due to a communications fault, it can use tne electronic signals passed v ia the second, third or fouπh ECL s 20. 30 and 40 respectivelv An advantage gained from this layout is that identical signals from the input unit 50 and/or sensors 65. 70. 80 and 90 are available to all parts of the system 5 at the same -o- time. This simplifies the error-detection task, as when correctly operating, all ECUs can perform identical operations on identical signals, and any differences indicate a fault. It w ill be appreciated that alternative embodiments to the one descobed above ": possible Although four nodes and ECUs are shown in FIG. 1. it w ill be appreciated that the invention applies to at least two nooes and at least tw o control means ( ECU) For example, a single rear suspension ECU could be used to replace the third and fouπh EC s 30 and 40. whereby the single rear suspension ECU would be coupled to the third anc r uπh suspension actuators 35 and 45 respective!) Referπng now to FIG. 2. there is shown a fault-tolerant steeπng system 105 for a v ehicle (not shown), including first, and second steeπng nodes having electronic control units (ECUs) 120. and 130. which are distobuted in mutually remote locations the v ehicle. Eacn of the first 120 ana second 130 ECUs are coupled to associated first, and second steeong actuators 125 and 135. respectively. Each steeong actuator is aoanged such that either can carry out the required actuation for the whole system in the event that the other fails. The first 120 and second 130 ECUs are also each coupled to first and second buses 107 and 108, respectively. An user operated input unit 115 provides an input signal to the first 120, and second 130 ECUs via the first 107 and second 108 buses. The user operated input unit 1 15 preferably composes a sensor 1 15, shown in FIG. 2 as a steeπng wheel sensor. Each of the ECUs 120. and 130 receives an input signal from the input The first and second buses 107 and 108 respectively are substantially identical anc are both arranged to provide synchronous signals according to a Time Division Multiple Access scheme ( TDMA) or similar Hign level functions ot cuoent steeπng svstems may be integrated into the sv stem 5 v ia a (high level) ECU 14υ coupled to the buses 107 and 108. or by a gateway to an ECU ( not shown ) The first 120 and second 130 ECUs can operate independently from each other if required, and are each able to provide a processed result signal to the associated steeπng actuator 125 and 135 in response to the input signals received from the input unit 115. In this way a basic steeπng function is achieved, which is the minimum required for safe operation, not necessaπly including higher level functions such as vehicle stability management. The provision of first and second buses 107 and 108 provides fault- tolerance in the case of a problem occumng therein. In addition, each of the first 120 and second 130 ECU performs a similar aigoothm using the same input signal recei ed from the input unit 1 1 5. and provides the input and the result signals to the other ECU In this way each ot tne first 120 and second 130 ECUs can detect incorrect operation bv compaong its recεiv ed input signals and result signals with the input and result signals received from the other ECU In the preferred embodiment, a third additional ECU 1 10 is coupled between the input unit 115 and the first 107 and second buses 108. The third ECU operates in a similar wav to that of the first 120 and second 130 ECUs in that it performs a similar aigoothm using the same input signal received from the input unit 1 15 to generate a result signal, and provides the input and the result signals to the other ECUs. In this way each of the first 120, second 130 and third 1 10 ECUs can detect incorrect operation by comparing its received input signals and result signals with the input and result signals received from the other ECU. The third ECU 110 is arranged in such a way such that if it is faulty, the input signal from the input unit 1 15 can still be transmitted to the first 120 and second 130 ECUs. In the preferred embodiment, as three ECUs are available to check the same signals, it is possible to not only detect that there is a problem somewhere in the system 105. but also to identify the faulty ECU. A faulty ECU can therefore be identified, either by itself, or by the maioπty of the ECUs in the system 105 via a v oting procedure, vvnerebv tne ECU having the most different results compared to the other ECUs is considered to be faulty. After a fault has been identified, appropπate action can be taken, such as logging the fault, running diagnostics, or resetting or disabling the node If an ECU is disabled due to a fault, the system 105 can be aoanged such that the mam steeπng function will be re- distπbuted across the operating EC s As each ECU checks its operation against the other ECUs. faults can be detected that mav be undetectable by using a simpler self-test type of checking m isolation. For example, an ECU may exhibit a fault where it decodes the input signals from the input unit 115 incorrectly, but the decoded value is still withm the allowed range. The ECU would pass -3- a self-test, and act on the faulty data if no other tests were performed, but with the descobed checking against other ECUs, the incorrect data would be detected. .An advantage gamed from this layout is that identical signals from the input unit 1 15 are available to all pans of the system 105 at the same time. This simplifies the error- detection task, as when correctly operating, all ECUs can perform identical operations on identical signals, and anv differences indicate a fault. Referπng now to FIG. 3. there is shown a fault-tolerant electronic vaive control sv stem 205 for a vehicle (not shown ). The valve control system shown includes a first, second, and third node each having an electronic control unit ( ECU) 220. 230 and 240, which mav be distobuted in a position proximate or locally to the cylinders in the vehicle. Each of the first, second and third ECUs are coupled to associated first 225. second 235 and third 245 valve actuators, or set of valve actuators, respectively. Each valve actuator is arranged such that any one ECU/valve actuator can carry out the required actuation for the whole system in the event that other ECU/valve actuators fail. It will be appreciated that any greater number (n) of nodes and or associated ECUs and valve actuators may be used in this configuration, for example as required in an n-cylinder engine. The first 220, second 230, and third (nth) 240 ECU are also each coupled to first and second buses 207 and 208 respectively. The fault-tolerant electronic combustion cylinder valve control system 205 also includes an input node for receiving an input signal. An input unit 215 may provide the input signal to the first, second, and third (nth) ECU via the first 207 and second 208 bus. The input unit preferably composes, for example, a sensor 215, shown in the figure as a combustion and dover sensor, and each of the ECUs 220. 230 and 240 receives an input signal from the input unit 215. The first and second buses 207 and 208 respectively are substantially identical and are both arranged to provide fast synchronous signals according to a Time Division Multiple Access scheme (TDMA) or similar. High ievel functions of current powertrain systems may be integrated into the system 205 via a ( high level) ECU 250 attached to the buses 207 and 208. or by a gateway to an ECU (not shown). The first 220. second 230. and third (nth) 240 ECUs can operate independently from each other if required, and are able to provide a processed result signal to the associated valve actuator 225, 235 or 245 in response to the first signals received from the input unit 215. In this way a basic valve control function is achieved, which is the minimum required for safe operation, not necessarily including higher level functions such as emissions control or torque adjustment control. The provision of first and second buses 207 and 208 provides fault-tolerance m the case of a problem occurong therein. In addition, each of the first 220. second 230. and third 240 (nth) ECUs performs a similar aigoothm using the same first signals received from the input unit 215 and provides the first signals and the result signals to the other ECU's. In this way each of the first, second, and third (nth) ECUs can detect incorrect operation by compaong its received first signals and result signals with those of the other ECUs. In a preferred embodiment, an additional ECU 210 is coupled between the input unit 215 and the first 207 and second 208 buses. The additional ECU operates in a similar manner to that of the first 220, second 230, and third (nth) ECUs in that it performs a similar algorithm using the same input signal received from the input unit 215 to generate a result signal, and provides the input and result signals to the other ECUs. In this way, each of the first, second and third ECUs can detect incorrect operation by comparing its received input signals and result signals with the input and result signals received from the other ECUs. The additional ECU 210 is arranged in such a way such that if it is faulty, the input signal from the input unit 215 can still be transmitted to the first 220, second 230. and fourth (nth) 240 ECUs. As there are multiple ECUs that are available to check the same signals, it is possible to not only detect that there is a problem somewhere m the system 205. but also to identify the faulty ECU. A faulty ECU can therefore be identified, either by itself, or by the majooty of the ECUs in the system 205 via a voting procedure, whereby the ECU having the most different results compared to the other ECUs is considered to be fault} After a fault has been identified, appropoate action can be taken, such as logging the fault, running diagnostics, or resetting or disabling the node. If an ECU is disabled due to a fault, the system 205 can be arranged such that the mam cylinder valve control could be compensated for by the other operating ECU's. As each ECU checks its operation against the other ECUs. faults can be detected that may be undetectable by using a simpler self-test type of checking in isolation. For example, an ECU may exhibit a fault where it decodes the received signals from the input unit 215 incorrectly, but the decoded value is still within the allowed range. The ECU would pass a self-test, and act on the faulty data if no other tests were performed, but ith the descπbed checking against other ECUs. the incorrect data would be detected An advantage gamed from this layout is that identical signals from the input unit 215 are available to all parts of the system 205 at the same time This simplifies tne error- detection task, as when correctly operating, all ECUs can perform identical algoπthmic operations on identical signals, and any differences indicate a tault It will be appreciated that alternative embodiments to those descπbed above are possible

Claims: Claims 1 A fault tolerant system for a vehicle, composing. an input node for receiving an input signal: and at least two nodes coupled to the input node, each node being aoanged to control at least one actuator, each node having control means aoanged for processing the input signal to provide a second signal for controlling the at least one actuator, and to provide a plurality of third signals to the at least one other control means, the third signals being expected second signal results of the at least one other control means, wherein each control means is arranged to compare the second signal with the third signals received from the at least one other control means such that errors detected between the second and third signals indicate faults in the at least two control means. 2. The system of claim 1 wherein upon detection of a fault, each control means uses a voting scheme to determine which of the second and third signals is to be used as a fourth signal to control each of the actuators. 3. The system of claim 2 wherein each control means is also arranged to transmit the fourth signal to the at least one other control means, in order to verify whether the voting scheme has been used correctly. 4 The system of any preceding claim wherein the at least two nodes are distobuted in mutually remote locations in the vehicle. 5. The system of any preceding claim wherein the input signal is adapted such that it is transmitted to the at least two nodes m a synchronous manner 6. The system of any preceding claim w herein the input signal is re-transmitted by each of the control means, for further fault detection. A fault tolerant suspension system for a v ehicle composing the system of an}' preceding claim composing three nodes and wherein the actuators are suspension actuators, each node being arranged to control one of three suspension actuators 8. The system of claim 7 further composing first and second input nodes, the first input node for receiving an input signal from an user operated input unit and the second mput node for receiving an input signal from a sensor, wherein the control means of each node is arranged to process the input signals received at the first and the second input nodes to provide the second signal. 9 The system of claim 8 further composing third, fourth and fifth input nodes, the third, fourth and fifth input nodes for receiving input signals from second, third and fouπh sensors respectiv ely. the sensors being aoanged to detect changes in motion of the vehicle, and wherein the control means of each node is aoanged to process the input signals received at the first, second, third, fourth and fifth input nodes to provide the second signal. 10 A fault tolerant steeπng system for a vehicle comprising the system of any one of claims 1 to 6. wherein the actuators are steeπng actuators and the system further composes an user operated mput unit aoanged to provide the input signal m response to operation thereof. 11. The system of claim 10 comprising three control means, a first control means being coupled to a first steering actuator, a second control means being coupled to a second steering actuator and a third control means being coupled to the first and second control means and the user operated input unit, wherein upon detection of a fault, each of the control means uses a voting scheme to determine which of the second and third signals is to be used as a fourth signal to control each of the first and second steeong actuators. 12. The system of claim 1 1 wherein each control means is also aoanged to transmit the fourth signal to the at least two other control means, m order to v erify w hether the voting scheme has been used correctly 13 A fault tolerant electronic v alve control system for a v ehicie composing the system of any one of claims 1 to 6 comprising three nodes and wherein the actuators are v alv e actuators, each node being aoanged to control one of three v alve actuators

Inventors: DUNLOP JOHN KENNEDY, JORDAN MARK JOHN, LYNAS STEPHEN, MAIOLANI MARK, MATTHEWS WILLIAM STEWART, DUNLOP, JOHN, KENNEDY, JORDAN, MARK, JOHN, LYNAS, STEPHEN, MAIOLANI, MARK, MATTHEWS, WILLIAM, STEWART
Applicants: DUNLOP JOHN KENNEDY, JORDAN MARK JOHN, LYNAS STEPHEN, MAIOLANI MARK, MATTHEWS WILLIAM STEWART, MOTOROLA LTD, DUNLOP, JOHN, KENNEDY, JORDAN, MARK, JOHN, LYNAS, STEPHEN, MAIOLANI, MARK, MATTHEWS, WILLIAM, STEWART, MOTOROLA LIMITED
Application year: 2000
Main classification: B60R
IPC codes: B60G17