Browse Topic: Drive-by-wire
While many observers think that autonomy is right around the corner, there many unsettled issues. One such issue is availability, or how the vehicle behaves in the event of a failure of one of its systems such as those with the latest “by-wire” technologies. Handling of failures at a technical actuation level could involve many aspects, including time of operation after first fault, function/performance after first fault, and exposure after first fault. All of these and other issues are affected by software and electronic and mechanical hardware. Drive-by-wire and Automated Driving System Availability discusses the necessary systems approach required to address these issues. Establishing an industry path forward for these topics will simplify system development and provide a framework for consistent regulation and liability, which is an enabler for the launch of autonomous vehicles. Click here to access the full SAE EDGETM Research Report portfolio.
ABSTRACT Teleoperated ground vehicles are an integral part of the U.S. Army and Marine Corps long range vision and a key transition technology for fully autonomous vehicles. However, the combination of marginally-stable vehicle dynamics and limited perception are a key challenge facing teleoperation of such platforms at higher speeds. New technologies for enhancing operator perception and automatically detecting and mitigating rollover risk are needed to realize sufficient safety and performance in these applications. This paper presents three rollover mitigation concepts for high speed teleoperation of heavy tactical vehicles, including model-predictive warning, negative obstacle avoidance, and reactive brake controls. A modeling and simulation approach was used to evaluate these concepts within the Autonomous Navigation Virtual Environment Laboratory (ANVEL). Vehicle models for both the M1078 cargo truck and RG-31 MRAP were used throughout concept evaluation over terrain ranging from urban highway to off-road conditions with more complex topography.
ABSTRACT L-3 Combat Propulsion Systems (L-3CPS) and Kinetics Drive Solutions (Kinetics) have teamed together to present this paper that discusses infinitely variable transmission technologies with high gear ratio & efficient steering systems for cross-drive transmissions across a family of combat vehicles. Traditionally, cross-drive transmissions for tracked vehicles are very rigid systems, which are tailored for a specific application or vehicle weight class. This becomes a problem throughout the vehicle’s lifecycle, as vehicle weights continue to grow when armor and other systems are added to protect and support the war-fighter. Increased weight leads to degraded vehicle mobility performance. To regain the vehicle mobility performance more power is needed at the vehicle sprockets. Traditionally this is accomplished by increasing the engine power of the propulsion system, which requires an increased transmission size for higher input and output torques, resulting in increased losses and decreased power to sprocket. This traditional approach incurs significant hardware and potential design costs when there is a need to upgrade a tracked vehicle’s power pack. L-3CPS and Kinetics believe there is a better way. A Hydro-Mechanical Infinitely Variable Transmission (HMIVT) closely integrated with electronic generator(s) and motor(s) that is packaged in a modular architecture that has the ability to adapt to a number of vehicle classes and weights is proposed. To address the challenge a systems engineering approach will yield a propulsion system having better power density (sprocket power / propulsion system volume) than traditional propulsion systems. A high efficiency HMIVT core will be used as the basis for the scalable and the modular configuration, allowing the engine to operate within its most efficient operating band while having the ability to adapt to changing vehicle weights and applications. The paper will discuss a building block concept for both current and future vehicle power classes from 750hp thru 1500hp. Benefits to this approach include; Open Architecture, Improved acceleration, Dynamic Braking, Scalability, Redundancy, Drive by Wire, Upgradability, and Future Growth/Optimization.
This paper presents a simultaneous longitudinal and lateral motion control strategy for a full drive-by-wire autonomous vehicle. A nonlinear model predictive control (NMPC) problem is formulated in which the nonlinear prediction model utilizes a spatial transformation to derive the dynamics of the vehicle about the reference trajectory, which facilitates the acquisition of the tracking errors at varying speeds. A reference speed profile generator is adopted by taking account of the road geometry information, such that the lateral stability is guaranteed and the lane guidance performance is improved. Finally, the nonlinear multi-variable optimization problem is simplified by considering only three motion control efforts, which are strictly confined within a convex set and are readily distributed to the four tires of a full drive-by-wire vehicle. Simulation results demonstrate the capability of the proposed controller to follow the reference trajectory while adjusting the vehicle speed automatically.
Development of conceptual drive-by-wire ECU for electric vehicle conversion (EVC) can be designed by means of a low cost and time saving model based process. This is done by employing MATLAB scripted programs to systematically compute the power flow regime of the electric vehicle propulsion and response to dynamic loads. In this particular design, vehicle data and modification of simplified federal urban driving cycle (SFUD) were the two main inputs for driving simulation. As a result, the simulation was capable to predict various EVC characteristics and design parameters, such as driving range, torque-speed characteristics, and motor power usage. Output obtained from simulation were employed as design criteria to set up drive-by-wire software and ECU hardware functions, which are driving modes, torque set point for EVC electric propulsion in all four quadrants. EVC functions also have potential benefits in the improvement of vehicle drivability to suit a driver's individual preference.
Vehicle manufacturers currently use Ethernet for fast batch transfers when updating software in ECUs in a vehicle. But Ethernet is also planned for real-time traffic as well; in the short term future for streaming of video and audio and potentially in the long term also for Drive-by-wire functions. Ethernet today uses the same frame format as the original Ethernet from the 1970s did but except from that it bears little resemblance to its original form. Ethernet today uses switches and hence the argument often raised against its use for carrying hard real-time traffic - that the shared medium can cause unbounded delay due to collisions - is not applicable today. In addition, normal Ethernet switches today support prioritization of traffic which allows an engineer to assign a high priority to urgent time-critical traffic so that its queuing delay is not affected by lower priority (supposedly less time-critical) traffic. Although the high bit-rate and the ability to control queuing delays thanks to prioritization are attractive for carrying real-time traffic, this alone cannot guarantee that real-time requirements are fulfilled. It is necessary to prove with mathematical rigor that given a traffic model and given the topology and configuration of the network, all real-time requirements will be met. Such proof techniques are known for the CAN bus and they have been adopted in design tools. Such proofs are also known for star networks based on switched Ethernet for simple traffic models but no design tool is currently based on them. Therefore, in this paper, in order to help designing this kind of analysis tool, we list desired functionalities of a tool for proving that timing requirements are fulfilled, and discuss important considerations for the analysis. It should support the ability to analyze multi-hop traffic over switched Ethernet networks and allow designers great freedom in how flows are described in order to reduce pessimism of the analysis due to modeling.
Automakers currently use Ethernet for fast batch transfers when updating software in ECUs in a vehicle. But Ethernet is also planned for real-time traffic as well; in the short term future for streaming of video and audio and potentially in the long term also for Drive-by-wire functions. Ethernet today uses the same frame format as the original Ethernet from the 1970s did but except from that it bears little resemblance to its original form. Ethernet today uses switches and hence the argument often raised against its use for carrying hard real-time traffic - that the shared medium can cause unbounded delay due to collisions - is not applicable today. In addition, normal Ethernet switches today support prioritization of traffic which allows an engineer to assign a high priority to urgent time-critical traffic so that its queuing delay is not affected by lower priority (supposedly less time-critical) traffic. Although the high bit-rate and the ability to control queuing delays thanks to prioritization are attractive for carrying real-time traffic, this alone cannot guarantee that real-time requirements are fulfilled. It is necessary to prove with mathematical rigor that given a traffic model and given the topology and configuration of the network, all real-time requirements will be met. Such proof techniques are known for the CAN bus and they have been adopted in design tools. Such proofs are also known for star networks based on switched Ethernet for simple traffic models but no design tool is currently based on them. Therefore, in this paper, we list desired functionalities of a tool for proving that timing requirements are fulfilled. It should sport the ability to analyze multihop traffic over switched Ethernet networks and allow designers great freedom in how flows are described in order to reduce pessimism of the analysis due to modeling.
Efficient integration of mechanics and microelectronics components is nowadays a must within the automotive industry in order to minimize integration risks and support optimization of the entire system. We propose in this work a cross domain co-simulation platform for the efficient analysis of mechatronic systems. The interfacing of two state-of-the-art simulation platforms provides a direct link between the two domains at an early development stage, thus enabling the validation and optimization of the system already during modeling phase. The proposed cross-domain co-simulation is used within our TEODACS project for the analysis of the FlexRay technology. We illustrate using a drive-by-wire use case how the different architecture choices may influence the system.
For driver assistant systems and drive-by-wire architectures fault detection and diagnosis are essential parts. Fault detection using parity equations is a well known approach which can be implemented in a straightforward way. Especially for fault diagnosis of vehicle sensors good isolating patterns for the interpretation of the residuals are available. However, in critical driving situations false alarms can occur, which may compromise the efficiency of safety relevant stability systems. In this paper a method is presented which reliably detects critical driving situations utilizing the estimated nominal cornering stiffness. The instantaneous cornering stiffness is estimated using the sideslip angle obtained by an observer. Using this quantity the nominal cornering stiffness can be estimated in order to discern the linear and nonlinear region of the tire model. In the nonlinear region false alarms are likely to occur and simple fault detection using parity equations cannot be used. Utilizing this approach, false alarms of the fault detection for the sensors of lateral acceleration, yaw rate, and steering angle can be avoided. The proposed fault detection and diagnosis concept clearly indicates the validity of the detection, and the performance is demonstrated with measurement data.
This paper reviews the development and application of an in-vehicle programmable drive-by-wire throttle controller. The system is comprised of commercially available hardware and utilizes a laptop PC for control. Real-time control feedback is achieved through integration with the vehicle CAN bus. As a result, the system delivers intelligent, precise, and highly repeatable throttle control for a wide variety of in-vehicle tests. Ultimately, this system serves as a great aid to the test engineer by eliminating driver variation, thus leading to superior test execution and straightforward data analysis.
Bus systems like CAN or FlexRay allowed great advances in automotive electronics over the last 20 years. In order to function in an environment which requires the communication medium to tolerate one safety-relevant fault, these bus systems require a second, redundant bus to act as a backup for the original unit. With the network approach presented in this paper (SafeNet) it is possible to use the network intrinsic redundancy to keep the network fail-safe after at least one safety relevant fault in the network. To ensure this, messages are relayed to every node in the network. Even though the message delivery times in the network are not deterministic, it is shown that it is suitable for safety-relevant applications like drive-by-wire. Due to the simple point-to-point connections used to connect the nodes, high speeds can be achieved. The network approach is compared to both CAN and FlexRay under different aspects.
The demand for drive-by-wire, pre-crash warning and many other new features will require high bandwidth from the future in-vehicle networks. One way to satisfy the high bandwidth requirement of future vehicles is to use a higher bandwidth bus or multiple busses. However, the use of a higher bandwidth bus will increase the cost of the network. Similarly, the use of multiple buses will increase cost as well as the complexity of wiring. Thus, neither option is a viable solution. Another option could be the development of a higher layer protocol to reduce the amount of data to be transferred. The higher layer protocol could be acceptable provided it does not increase the message latencies. The cost of implementing the protocol will be marginal because it can be done by making changes in software. Various data reduction protocols are available in the literature. We have made changes in the existing data reduction protocols to improve the performance of the protocol. Our paper will explain the improved protocol in detail and compare its performance with that of other protocols. The performance of our protocol will be shown in terms of message latency, message throughput and bus utilization.
This paper describes the design of a drive-by-wire system for a commercial lift truck using the FlexCAN communication architecture. FlexCAN is a recently developed architecture based on the CAN protocol to support deterministic and safety-critical applications. The main features of FlexCAN are its simplicity and ready implementation based on COTS CAN components. The main steer-by-wire design tasks are listed and a description of how each of the tasks was accomplished using the FlexCAN architecture is detailed. A performance evaluation of the design is included.
Embedded automotive applications such as drive-by-wire in cars require dependable interaction between various sensors, processors, and actuators. This paper addresses the design of low-cost communication networks guaranteeing to meet both the performance and fault-tolerance requirements of such distributed applications. We develop a fault-tolerant allocation and scheduling method which maps messages on to a low-cost multiple-bus system to ensure predictable interprocessor communication. The proposed method targets time-division multiple access (TDMA) communication protocols. Finally, we present a case study using some advanced automotive control applications to show that our approach uses the available network bandwidth efficiently to guarantee message deadlines.
Many next-generation automotive control systems, such as brake-by-wire, will feature the replacement of mechanical linkages between the driver and vehicle actuators by sensors communicating with computer-controlled electromechanical actuators. For such systems, redundancy is often employed to achieve the required fault tolerance and reliability. In this paper, we investigated the effect of hardware redundancy on the timing, control performance and reliability of an automotive drive-by-wire system. From an initial, minimal system design, we then added redundancy to provide fault-tolerance in the most critical areas of the system. To investigate if the software architecture had an influence on the effects of this redundancy, we implemented two different approaches to the software design for each implementation. We then used a Hardware-In-the-Loop (HIL) testing facility to record performance metrics for each of the four implementations. These metrics are presented and discussed. Finally, we applied reliability modeling techniques to consider the changes in overall system reliability that can be expected between systems.
The Diesel engine popularity has been increasing for the last years, mainly in Europe, where the Diesel passenger cars fleet surpassed the petrol one. Such popularity is not only a result of fuel consumptions benefits, but also a result of a combination of all engine attributes performance including powertrain NVH and drivability. Thus, the common rail technology must provide capabilities to improve the attributes for this competitive and demanding market. This paper intends to idealize the drive-by-wire response in Diesel engines, which is a technological feature that contributes to achieve the customer vehicle performance feel and drivability expectation.
The introduction of drive-by-wire systems into modern vehicles has generated new challenges for the designers of embedded systems. These systems, based primarily on microcontrollers, need to achieve very high levels of reliability and availability, but also have to satisfy the strict cost and packaging constraints of the automotive industry. Advances in VLSI technology have allowed the development of single-chip systems, but have also increased the rate of intermittent and transient faults that come as a result of the continuous shrinkage of the CMOS process feature size. This paper presents a low-cost, fault-tolerant system-on-chip architecture suitable for drive-by-wire and other safety-related applications, based on a triple-modular-redundancy configuration at the processor execution pipeline level.
This paper will describe the technical capabilities and vehicle design freedom made possible by drive-by-wire powertrain and chassis control systems, using SKF's Smart Electro-Mechanical Actuating Unit (SEMAU) technology. It will describe the advantages to the vehicle users and vehicle manufacturers of integrating electronic controls into the previously mechanically, hydraulically, and pneumatically actuated function and also show how mechatronic solutions can contribute to these advantages. The paper will refer to the FILO, NOVANTA, and GM Hy-wire concept vehicles, which utilize “by-wire” technology, in order to illustrate these advantages.
Electronics is driving 90% of the functional innovation in vehicles which is generating a demand for more (single function) control units to realise the new feature content. Adding such extra ECU's cannot be supported without limit due to packaging space on the vehicle and the significant increase in electrical system complexity. Also, the need for functional integration (between ECU's) is necessary to satisfy key market trends for improved vehicle safety and drive-by-wire capability. This need would not be met by lots of single function ECU's which is leading to a demand for new in-vehicle network architectures. At the same time, the OEM's are looking to define the vehicle “brand image” through advanced software applications which need to be integrated with supplier software within multiple ECU's. This paper describes the impact on vehicle electrical networks of the multiplying ECU problem (driven by the multiple sensor and vehicle control system technologies) and describes possible system architectures to support the increasing demand for functional integration. An approach to support the evaluation of network architectures shall be illustrated using the development of a prototype network vehicle controller that provides a high performance microprocessor (>500MIPs) and high speed network interfaces.
The automotive industry is moving ahead to introduce drive-by-wire (DBW) electronic systems to replace mechanical controls and linkages that have changed little since cars were first introduced. Electronic drive-by-wire systems offer enormous potential to improve vehicle performance and safety, but matching the dependability of simple mechanical components with electronics will be a challenge. Highly dependable electronic controls require a fault-tolerant approach with both a primary and a backup system as a minimum. Aircraft fly-by-wire systems go beyond this, using triple and quadruple redundant electronics to tolerate more than one failure during the same flight. Automobile drive-by-wire must also provide some capability to allow the car to be driven safely to a repair facility after a failure occurs. This paper examines some possible drive-by-wire systems architectures, presents a mathematical analysis of the predicted dependability (expressed as the probability the system will fail in a given time period) of these alternatives and investigates the impact of how the vehicle is operated and maintained on its dependability. Architectural alternatives considered include both dual and triple redundant systems. The mathematical analysis builds on techniques developed to analyze aircraft systems using Markov reliability modeling. The uncertainty associated with such predictions will be discussed along with comparisons to acceptable risk levels for other established technologies.
A design method for ultra-dependable control-by-wire systems is presented here. With a top-down approach, exploiting the system's intrinsic redundancy combined with a scalable software redundancy, it is possible to meet dependability requirements cost-effectively. The method starts with the system's functions, which are broken down to the basic elements; task, sensor or actuator. A task graph shows the basic elements interrelationships. Sensor and actuator nodes form a non-redundant hardware architecture. The functional task-graph gives input when allocating software on the node architecture. Tasks are allocated to achieve low inter-node communication and transient fault tolerance using scalable software redundancy. Hardware is added to meet the dependability requirements. Finally, the method describes fault handling and bus scheduling. The proposed method has been used in two cases; a fly-by-wire aircraft and a drive-by-wire car.
The Controller Area Network (CAN) has seen enormous success in automotive body and powertrain control systems. However, there is a change in emphasis arising in the industry in which CAN is seen as too powerful and expensive for simple digital body control applications, but not robust or fast enough for more safety critical applications such as the envisaged Drive-by-Wire systems of future passenger cars. The emerging protocols Local Interconnect Network (LIN), the Time Triggered Protocols (TTP/A, TTP/C), Time Triggered CAN (TTC) and Byteflight are examined in terms of their application and likelihood for future success. The paper is concluded with comments concerning a newly announced protocol known as FlexRay.
Nearly every area of vehicle electronics is experiencing a design and implementation revolution. Drive-by-wire concepts, controller area networks, and “on-line” information systems are rapidly changing the way we view vehicle electronics. Advancements in technology enable improvements or even revolutionary changes in the way products are designed. Enhancements in semiconductor technology are enabling an evolutionary change in the design of products for all types of vehicles. Electrical systems are supporting the movement towards higher voltages, more features, and more power. Today, heavy duty signaling applications may have as many as 20 bulbs connected to the flasher, forcing designers to look towards higher reliability, solid state switching methods.
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