Abstract Brake systems are strongly related with safety of vehicles. Therefore a reliable design of the brake system is critical as vehicles operate in a wide range of environmental conditions, fulfilling different security requirements. Particularly, countries with mountainous geography expose vehicles to aggressive variations in altitude and road grade. These variations affect the performance of the brake system. In order to study how these changes affect the brake system, two approaches were considered. The first approach was centered on the development of an analytical model for the longitudinal dynamics of the vehicle during braking maneuvers. This model was developed at system-level, considering the whole vehicle. This allowed the understanding of the relation between the braking force and the altitude and road grade, for different fixed deceleration requirement scenarios. The second approach was focused on the characterization of the vacuum servo operation.
Abstract The disk spring offers the potential of significant weight savings when designed with continuous fiber reinforced composite materials. The internal stresses in a disk spring are ideally suited for composite material application due to their superior resistance to in-plane and bending stresses. In this study, a composite laminate disk spring is designed, analyzed and fabricated to take advantage of the low specific strength and weight and high damage tolerance of composite laminates. The design of the disk composite spring considers effects of the laminate stacking sequence and the geometric variables on the disk spring's mechanical performance. A continuum damage finite element analysis approach is used to understand the damage initiation and evolution as a function of applied load. Experimental analysis and a progressive damage analysis based on virtual crack closure technique are performed to evaluate the damage tolerance of the disk spring under fatigue loadings.
Abstract Aircraft anti-skid brake control system is considered one of the most complex aircraft systems whose performance depends not only on subsystem parameters but rather on many other external conditions and physical parameters which are difficult to control and predict. Over the years aircraft brake control system performance and fault diagnostics have been simulated and analyzed from various aspects. Based on the task to enhance aircraft brake control system diagnostic methods, this article presents one approach to mathematical modeling and a numeric identification method of the hydro-mechanical brake control components. For any complex system behavioral or performance analysis approach, system modeling and simulation are the most common tools. Most often, the complete system model is unknown, and only simple segments of the unknown system or a small number of subsystem components may be known in a form of transfer function with static and dynamic characteristics.
There are a number of numerical and experimental studies of the aerodynamic performance of wheels that have been published. They show that wheels and wheel-housing flows are responsible for a substantial part of the total aerodynamic drag on passenger vehicles. Previous investigations have also shown that aerodynamic resistance moment acting on rotating wheels, sometimes referred to as ventilation resistance or ventilation torque is a significant contributor to the total aerodynamic resistance of the vehicle; therefore it should not be neglected when designing the wheel-housing area. This work presents a numerical study of the wheel ventilation resistance moment and factors that affect it, using computational fluid dynamics (CFD). It is demonstrated how pressure and shear forces acting on different rotating parts of the wheel affect the ventilation torque. It is also shown how a simple change of rim design can lead to a significant decrease in power consumption of the vehicle.
As part of the aircraft certification process, landing gear has to be certified against particular risks such as bird and tyre impact cases. According to international aviation regulations, it has to be demonstrated that the landing gear is designed to ensure the capability for continued safe flight and landing after bird impact or after tyre impact resulting from wheel or tyre failure. Structural parts such as the down-lock mechanism must be validated against these requirements since their structural integrity is essential to ensure landing gear down-locking for landing and subsequent on ground movement. Recently, MESSIER-BUGATTI-DOWTY has been involved in the development of explicit analysis in support of bird and tyre impact justification. A model of the down-lock mechanism has been developed and a full scale test has been set up in order to demonstrate the validity of the analysis.
Power Consumption Analysis of a Flexible-Wheel Suspension Planetary Rover Operating upon Deformable Terrain
This study analyzes the power consumption of a specific Planetary Exploration Vehicle (PEV) subsystem known as Flexible-Wheel (FW) suspension, more specifically the interaction between a FW and the deformable terrain upon which it traverses. To achieve this a systematic and analytical calculation procedure has been developed, which culminates in the definition of three dimensionless properties to capture the FW-soil interaction. Aimed towards the design engineer participating in concept evaluation, and the control engineer conducting initial analyses, this study has found that the resistance coefficient for the interaction between a FW and the deformable terrain can, in general, be several orders of magnitude higher than the rolling resistance of a pneumatic tire operating upon rigid terrain.
A hydraulic-assisted power steering system on a vehicle has a steering pump which is directly driven from the engine continuously. In real world, the assistance from the steering pump is useful only while maneuvering. During a typical highway drive, assistance from this power steering pump remains unused for majority (76%) of the time; although the continuously rotating power steering pump keeps consuming energy from the engine. An electronic controller has been provided for the electro-magnetic pairing device of the power steering pump in order to provide assistance for steering based on driver demand only. The electromagnetic pairing device integrated on the steering pump can be made to engage/disengage based on the driver demand through the electronic controller.
Targets for reducing emissions and improving energy efficiency present the automotive industry with many challenges. Passenger cars are by far the most common means of personal transport in the developed part of the world, and energy consumption related to personal transportation is predicted to increase significantly in the coming decades. Improved aerodynamic performance of passenger cars will be one of many important areas which will occupy engineers and researchers for the foreseeable future. The significance of wheels and wheel housings is well known today, but the relative importance of the different components has still not been fully investigated. A number of investigations highlighting the importance of proper ground simulation have been published, and recently a number of studies on improved aerodynamic design of the wheel have been presented as well. This study is an investigation of aerodynamic influences of different tires.
Aerodynamic efficiency plays an increasingly important role in the automotive industry, as the push for increased fuel economy becomes a larger factor in the engineering and design process. Longitudinal drag is used as the primary measure of aerodynamic performance, usually cited as the coefficient of drag (CD). This drag is created mostly by the body shape of the vehicle, but the wheel and tire system also contributes a significant portion. In addition to the longitudinal drag created by the body and wheels, rotational drag can add an appreciable amount of aerodynamic resistance to the vehicle as well. Reducing power consumption is an especially vital aspect in electric vehicle (EV) design. As the world's first luxury electric sedan, the Tesla Model S combines a premium driving experience with an electric drivetrain package that allows for unique solutions to many vehicle subsystems.
First generation of Integrated Modular Avionics (IMA), currently onboard in aircraft type Airbus A380, A400M, or designed for Airbus A350, and whose principle was initially to introduce some common processing resources, had been developed in such a way to reduce the quantity of embedded equipment part number, and to harmonize the nature of the avionic units by minimizing the specificity of electronic equipment: thus, for instance, the number of processing units in the A380 is half that of previous LRU-based avionic generations.
Magneto-rhelological(MR) dampers are devices that use rheological fluids to modify the mechanical properties of fluid absorber. The mechanical simplicity, high dynamic range, large force capacity, lower power requirements, robustness and safe manner of operation have made MR dampers attractive devices for semi-active real-time control in civil, aerospace and automotive applications. Landing gear is one of the most essential components of the aircraft, which plays an extreme important role in preventing the airframe from vibration and excessive impact forces, improving passenger comfortable characteristics and increasing aircraft flight safety. In this paper, the semi-active system used in landing gear damping controller design, simulation, and the vibration test-bed are discussed and researched. The MR dampers employed in landing gear system were designed, manufactured and characterized as available semi-active actuators.
Advancements in Hardware-in-the-Loop Technology in Support of Complex Integration Testing of Embedded System Software
Automotive technology is rapidly changing with electrification of vehicles, driver assistance systems, advanced safety systems etc. This advancement in technology is making the task of validation and verification of embedded software complex and challenging. In addition to the component testing, integration testing imposes even tougher requirements for software testing. To meet these challenges dSPACE is continuously evolving the Hardware-In-the-Loop (HIL) technology to provide a systematic way to manage this task. The paper presents developments in the HIL hardware technology with latest quad-core processors, FPGA based I/O technology and communication bus systems such as Flexray. Also presented are developments of the software components such as advanced user interfaces, GPS information integration, real-time testing and simulation models. This paper provides a real-world example of implication of integration testing on HIL environment for Chassis Controls.
Influences of Different Front and Rear Wheel Designs on Aerodynamic Drag of a Sedan Type Passenger Car
Efforts towards ever more energy efficient passenger cars have become one of the largest challenges of the automotive industry. This involves numerous different fields of engineering, and every finished model is always a compromise between different requirements. Passenger car aerodynamics is no exception; the shape of the exterior is often dictated by styling, engine bay region by packaging issues etcetera. Wheel design is also a compromise between different requirements such as aerodynamic drag and brake cooling, but as the wheels and wheel housings are responsible for up to a quarter of the overall aerodynamic drag on a modern passenger car, it is not surprising that efforts are put towards improving the wheel aerodynamics.
The optimization of vehicle suspension kinematics characteristics is an important part in the chassis development. The current optimization algorithms for suspension kinematics parameters are certain optimization method. But vehicles to manufacture in large quantities are uncertainty in the structural parameters. Therefore, suspension kinematics characteristics are all uncertain parameters on vehicles. The paper explored an interval method to describe the uncertainty suspension kinematics characteristics and used improved interval Newton iteration method to optimize it. As we all know, some suspension kinematics characteristics are the curves. When the structural parameters are uncertain variables, these curves are uncertain variables curves.
This research paper addresses the ground vehicle reliability prediction process based on a new integrated reliability prediction framework. The integrated stochastic framework combines the computational physics-based predictions with experimental testing information for assessing vehicle reliability. The integrated reliability prediction approach incorporates the following computational steps: i) simulation of stochastic operational environment, ii) vehicle multi-body dynamics analysis, iii) stress prediction in subsystems and components, iv) stochastic progressive damage analysis, and v) component life prediction, including the effects of maintenance and, finally, iv) reliability prediction at component and system level. To solve efficiently and accurately the challenges coming from large-size computational mechanics models and high-dimensional stochastic spaces, a HPC simulation-based approach to the reliability problem was implemented.
In order to solve the reliability and security problems which are caused by the structural alteration of the traditional steering system, the fault-tolerant control method for the Electronic Control Unit of Steer-By-Wire system is studied in this paper. A hardware structure of SBW, with triple cores and dual motors is present. And one triple-loop control system and a triple-core control mechanism which is coordinated by distributed processing mechanism and voting mechanism are proposed too. The communication among steering feeling motor, steering motor and cores is achieved through FlexRay bus. The Hardware-in-loop Simulations test result shows that the reliability and safely of the Electronic Control Unit of Steer-By-Wire system is effectively improved.
In this paper a four independent wheel-steering system and its application on the HOST prototype are presented. The prototype is a heavy duty vehicle with four wheel motors controlled by wire, so that each wheel is mechanically not-linked to the other ones and has four degrees-of-freedom. Each wheel has an electric steering actuator to move the wheels around the steering axis, which is controlled by wire. The first part of the work deals with the model determination, reducing the four degree-of-freedom system into a one degree-of-freedom system. In the second part, the relationship between the rotations of each wheel and the linear movement of the electric steering is presented. In the third part the steering ratio is calculated and a parameter to reduce the slip angle is defined. In this way a four independent wheel steering model has been developed and applied to the specific characteristics of HOST.
Development of Endurance Testing Apparatus Simulating Wheel Dynamics and Environment on Lunar Terrain
This paper entails the design and development of a NASA testing system used to simulate wheel operation in a lunar environment under different loading conditions. The test system was developed to test the design of advanced nonpneumatic wheels to be used on the NASA All-Terrain Hex-Legged Extra-Terrestrial Explorer (ATHLETE). The ATHLETE, allowing for easy maneuverability around the lunar surface, provides the capability for many research and exploration opportunities on the lunar surface that were not previously possible. Each leg, having six degrees of freedom, allows the ATHLETE to accomplish many tasks not available on other extra-terrestrial exploration platforms. The robotic vehicle is expected to last longer than previous lunar rovers.
Scope of the DRESS project is to research, develop and validate a distributed and redundant electrical steering system technology for an aircraft nose landing gear. The new system aims to: • reduce system weight at aircraft level, replacing the current hydraulic actuation system with an electric one. • improve aircraft safety, achieving higher system redundancy levels compared to the current technology capabilities. This paper presents an outline of different activities occurring in the DRESS project and also shows preliminary results of the new system performance.
Integration of aircraft landing gear systems requires a high level of knowledge and understanding of these systems and how they contribute to aircraft performance. This paper considers a specific design requirement for the steering system. Failure of the steering system, resulting in the aircraft leaving the runway at high speed, can be considered hazardous or even catastrophic. The ability of the system to detect such a failure and take appropriate action is a key aspect of the design. This paper describes an aircraft level steering runaway failure analysis using an aircraft level mechanical and hydraulic control coupled simulation model. The aircraft level simulation model includes aircraft structure, weight and inertia. Appropriate loads and forces (engine thrust, aerodynamic forces, lift, drag) and moments are then applied. The model also includes nose and main landing gears, brakes and tires.
Power and Energy Balance for Model Validation and Reduction (PEMRA) – Frequency Coupling. Application on Aircraft System Models
Nowadays, numerical modeling/simulation is an essential tool. It is used in all the design stages in order to improve quality and to reduce costs and time-to-market. As models address increasingly multiphysics and complex phenomena throughout the V-cycle process, modelers are confronted, sooner or later, with the need for model reduction. This paper describes the set-up of a virtual prototyping platform and highlights the interest of integrating energetic aspects, which are used to compute new model reduction criteria. A similar energy approach, “MORA” using “Activity”, is already used by Bond Graphists in order to obtain the “Proper Model” ( and ). The methodology presented here (PEMRA: “Power & Energy -based Model Reduction Algorithm”), with new power and energy criteria, makes it possible to obtain a simpler and more accurate reduced model than with MORA methodology, while improving the system's energy information.
The purpose of this research is to characterize the wear resistance of wheel treads made of polymeric woven and non-woven fabrics. Experimental research is used to characterize two wear mechanisms: (1) external wear due to large sliding between the tread and rocks, and (2) external wear due to small sliding between the tread and abrasive sand. Experimental setups include an abrasion tester and a small-scale merry-go-round where the tread is attached to a deformable rolling wheel. The wear resistance is characterized using various measures including, quantitatively, by the number of cycles to failure, and qualitatively, by micro-visual inspection of the fibers’ surface. This paper describes the issues related to each experiment and discusses the results obtained with different polymeric materials, fabric densities and sizes. The predominant wear mechanism is identified and should then be used as one of the criteria for further design of the tread.
The potential benefits offered by alternative aircraft taxiing methods without the use of the aircraft's main engines have attracted substantial interest in recent years from the aviation industry as well as the general public. Amongst the proposed aircraft taxiing methods, the electric wheel-drive concept has received the most media attention. As part of ongoing research and development into the More Electric Aircraft (MEA), a study has been conducted to examine the technical feasibility of an electric wheel-drive taxiing system using publicly available aircraft and runway coefficient data. The study shows the potential for overall mission fuel burn reductions, particularly for short haul aircraft with a relatively long taxi time.
The Effect of Wear Groove on Vibration and Noise of Aircraft Brakes: Theoretical and Experimental Evidence
The goal of this paper is to delineate recent experimental evidence that the presence of conforming surface wear groove tends to stabilize the vibration and noise response of aircraft brakes. This finding is consistent with an earlier theoretical study in which the contact between Carbon-Carbon (C/C) composite brake disks were assumed to be visco-elastic and through this assumption it was found that the existence of conforming grooves results in increasing dynamic stability of brake disk interaction. Therefore, the presumption of visco-elastic contact for C/C brakes seems to agree with the experimental observation in a subscale dynamometer. The present paper summarizes both theoretical analysis and the test results. In the tests C/C composites were heat treated for one hour at temperatures 1800°C and 2400°C, respectively. They were then subjected to frictional tests in a subscale aircraft brake dynamometer at 50 % relative humidity (RH) level.
This work is a contribution to the development of a 3-D space frame vehicle structure design and numerical optimization applied to a high performance roadster vehicle. , for this type of vehicle, a chassis must be as rigid and lightweight as possible in order to fulfill drivability (the degree of smoothness and steadiness of acceleration of an automotive vehicle) and maneuverability (the quality of being capable of maneuvering or changing position) requirements. Some difficulties in obtaining the optimum design by using analytical formulation are encountered, because this real structure is a complex geometry one. In this work a chassis design methodology that integrates a set of nature-inspired optimization tools developed under MATLAB® and finite element analysis using the commercial software ANSYS® is presented. Numerical results are reported, illustrating the success of using the presented methodology, as applied to the design optimization of a space frame vehicular structure.
Modeling and simulation of dynamic systems is not always a simple task. In this paper, the mathematical model of a 4 Degree Of Freedom (DOF) ride model is presented using a bond-graph technique with state energy variables. We believe that for the physical model as described in this research, the use of a bond-graph approach is the only feasible solution. Any attempt to use classical methods such as Lagrange equations or Newton's second law, will create tremendous difficulties in the transformation of a set of second order linear differential equations to a set of first order differential equations without violating the existence and the uniqueness of the solution of the differential equations, the only approach is the elimination of the damping of the tires, which makes the model unrealistic. The bond-graph model is transformed to a mathematical model. Matlab is used for writing a computer script that solves the engineering problem.
The pocket rocket definition is a small vehicle with a bigger engine. The result is a vehicle with better acceleration, top speed and speed recovery. This extra performance must be followed by improved lateral and longitudinal grip, faster steering response and also upgraded brakes. Based on a 1.0L popular vehicle, several changes were performed, transforming this family oriented vehicle in an enjoyable small sports car. The engine was changed to a production 1.8L, followed by upgrades in transmission, suspension, wheel & tires, brakes and powertrain integration.
The titanium is on excellent material for fabrication of aerospace springs in substituting to steels, due to its high corrosion resistance, 60% lower density, and lower elastic modulus. The production of the titanium alloys by powder metallurgy (M/P), starting from the elemental powders is a feasible route considering its lower costs and versatility. In this work, results of the Ti-3Al-8V-6Cr-4Mo-4Zr (β-C) and Ti-35Nb-7Zr-5Ta alloys production are presented. Samples were cold isostatic pressing (350 MPa) with subsequent densification by sintering at 1200, 1400 and 1500 °C, in vacuum. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. Density was measured by Archimedes method. It was shown that the samples were sintered to high densities and presented homogeneous microstructure.
Studying the Effect of Pad Contact Surface on the Frictional Behavior and Acoustic Noise Response for Heavy Duty Vehicle Brakes Using FAST Machine
The influence of the pad contact surface deformation for vehicle brakes on its frictional behavior and friction induced noise is presented in this paper. Friction composite samples of organic binder-type brake pad have been curried out at 17 MPa and 180 °C for heavy-duty applications. However, samples with different surface shapes (solid, drilled and grooved) have been formed and tested tribologically to satisfy suitable friction coefficient at low noise level. A FAST machine was used to find out the accurate friction response at steady frictional moment. Friction acoustic noise has been carried out on the test machine using the sound pressure level meter. Analyses of the obtained results showed that the feature of the pad material surface has a significant influence on the brake frictional stability and noise emission. The results also confirmed that; adding a groove to the brake lining in heavy-duty vehicles gives a better brake performance and hence it is highly recommended.
On the Design and Control of a New Generation of Reconfigurable Space Manipulators with Passive Joints
This work presents a new paradigm and a conceptual design for reconfigurable robots. Unlike conventional reconfigurable robots, our design does not achieve reconfigurability by utilizing modular joints. Rather, the robot is equipped with passive joints, i.e., joints without actuator or sensor, which permit changing the Denavit-Hartenberg parameters such as the link length and twist angle. The passive joints will become controllable when the robot forms a closed kinematic chain. Also, each passive joint is equipped with a built-in brake mechanism which is normally locked, but the lock can be released whenever the parameters are to be changed. Not only will such a manipulator have the versatility to perform different tasks but also it can be packed adequately within its designated space on the launch vehicle. Kinematics of such a robot is analyzed, and a stable control algorithm which can take the robot from one configuration to another is devised.