Browse Topic: Four wheel drive
Full state feedback offers theoretically guaranteed multi-axis stability, making it superior to conventional PID controllers. There is however one drawback, a full state controller has a mathematical difficulty if the B matrix is not square and thus not invertible. This is the case for helicopters with 6 degrees of freedom and 4 inceptors. Variations of linear quadratic regulators are a work around, however complexity dramatically increases. Best would be a direct solution to the original problem. This is the breakthrough result of this paper. This paper documents an approach which removes the analysis roadblock by partitioning the 6 x 6 system "A" matrix into two groups of 4 x 4 matrices. The 4x4 matrices are individually stabilized with full state gain matrices. One matrix is designated “Driver Matrix” which provides actuator commands. The other matrix is designated "Reference Matrix" which provides references. The two matrices are coupled together by requiring that the driver matrix follow references generated by the reference matrix. With each matrix individually stabilized, the coupled combination is also stabilized. Computation of flight dynamics states (u, v, w, p, q, r) is shared between the matrices. Initial results are very encouraging, showing an originally sluggish, heavy lift helicopter having now concise decoupled responses to pitch and roll commands. Stability derivatives are recomputed during flight allowing coverage over the whole flight envelope. A handling qualities task has been defined to relocate a 40 ft standard seaborne container directed by a pilot in a ground control station. Cooper Harper ratings of this task have demonstrated favorable Level 1 handling qualities if use is made of an automated lateral repositioning command.
Vehicle electrification has introduced new powertrain possibilities, such as the use of four independent in-wheel motors, enabling the development of control strategies that enhance vehicle safety and drivability. The development of a model capable of simulating vehicle behavior is fundamental for control system design. A high-fidelity model takes into account several parameters, such as vehicle ride height, track width, wheelbase, and others, making it possible to evaluate the vehicle’s behavior and allowing for prior validation of the design, thus contributing to improved vehicle safety and performance. In this context, this study presents a lateral dynamic model of a Formula 4WD vehicle with in-wheel motors, enabling the simulation and analysis of the vehicle’s behavior in cornering maneuvers. To achieve this, the complete lateral model is developed using MATLAB Simulink as the platform, incorporating the semi-empirical Hans Pacejka tire model, calculating yaw moment, and analyzing forces to accurately describe the vehicle’s dynamics.
This project presents the development of an advanced Autonomous Mobile Robot (AMR) designed to autonomously lift and maneuver four-wheel drive vehicles into parking spaces without human intervention. By leveraging cutting-edge camera and sensor technologies, the AMR integrates LIDAR for precise distance measurements and obstacle detection, high-resolution cameras for capturing detailed images of the parking environment, and object recognition algorithms for accurately identifying and selecting available parking spaces. These integrated technologies enable the AMR to navigate complex parking lots, optimize space utilization, and provide seamless automated parking. The AMR autonomously detects free parking spaces, lifts the vehicle, and parks it with high precision, making the entire parking process autonomous and highly efficient. This project pushes the boundaries of autonomous vehicle technology, aiming to contribute significantly to smarter and more efficient urban mobility systems.
After three years away from the U.S. market with its range-topping SUV, the Land Cruiser, Toyota unveiled the redesigned 2024 Land Cruiser in Salt Lake City on Aug. 1. The model, long known around the world for its durability and offroad credentials, arrives with the SUV competition hotter than ever. The company said the new model will start at around $55,000. The new Land Cruiser has just one engine option, the i-Force Max turbo 2.4-L four-cylinder hybrid that generates 326 hp and 465 lb-ft (630 Nm) that is routed through an 8-speed automatic transmission. All models are equipped with what Toyota classifies as a “full-time four-wheel-drive system” with a lockable center differential and an electronically controlled 2-speed transfer case to impart high- and low-range capability. Also standard is a lockable rear differential to apportion power in a 50/50 ratio across the rear axle.
If a mid-20th century engineer could time travel and see Magna's electric off-road powertrains, they might ask “why is the rear differential so gigantic?” But that's no differential. It's a powerful electric motor fully integrated into each front and rear axle for full 4x4 traction. And Magna said the system will “very likely” be seen on a production vehicle within a few years. At its 2023 tech day presentation, held at a Michigan offroad park and Magna International HQ in Troy, Mich., SAE Media had the opportunity to drive prototype vehicles offroad and sample Magna's in-cabin safety features.
CNH Industrial recently introduced what it says is the world's first autonomous-ready, battery-electric light utility tractor at its Tech Day in Phoenix, Arizona. The New Holland T4 Electric Power is another step in the company's vision for extensive electrification and autonomy across its lineup. The company said production would begin in late 2023 on the four-wheel-drive tractor. Its e-motor provides a continuous 75 hp (55 kW) and peaks at 120 hp (89 kW), with max torque of 236 lb-ft (440 Nm) and a top speed of 25 mph (40 km/h). All those performance figures - which are comparable to the many internal-combustion (IC) tractors in the light utility category - start with a 95-kWh battery pack. Engineers said the tractor's battery can power a full day of work for many mission profiles. That's largely because power is used on-demand and never at idle as with an IC-powered rig. If a mid-use charge is required, the battery can be charged to 100% capacity in about an hour with standard fast-charging systems.
With high integration, high efficiency and high flexibility, the front wheel independent Steer-by-Wire system (SbW) is a key link between autonomous vehicles and intelligent chassis technology, and is one of the current focused research in industry and academia. In this paper, a strategy for active control of steering geometry of the Steer-by Wire independent steering system is proposed based on the nonlinear three-step method and Ackermann geometry relationship with the control goal of improving the driving stability and handling performance of the vehicle. The control strategy takes the front wheel steering angle difference and yaw moment as the control variables, and tracks the expected side slip angle and yaw rate as the control objectives. A more accurate vehicle model, and a nonlinear tire model with a reference vehicle model, is used to design the three-step controller to improve the effectiveness of the steady-state control and reduce the system error. When designing the relationship between steering wheel angle and wheel angle, the relationship between vehicle speed and steering wheel angle was considered to improve the vehicle response. After the controller design was completed, a joint simulation of an electric four-wheel drive(4WD) vehicle under multiple operating conditions was conducted based on Simulink and Carsim platforms to verify the effectiveness of the controller. The longitudinal and lateral postures of the vehicle were coordinated and controlled using a transverse moment controller and a front wheel angle controller. The results show that the nonlinear three-step controller can effectively track the desired value of the control target, maintain the stability of the vehicle, and achieve active Ackermann steering geometry control under complex operating conditions.
An all-terrain vehicle (ATV) is capable of traveling on any kind of surface or terrain. It is built especially for extreme road conditions. High ground clearance and soft suspension springs are some of the characteristics of an ATV. The use of a four-wheel-drive (4WD) transmission in a light ATV is in high demand. Power on all four tires provides better traction and increases the off-roading capabilities of the ATV. The methodology described in the paper discusses the design and validation of a four-wheel driveline for a light ATV using various modeling and simulation software. Briggs and Stratton engine is coupled with a continuously variable transmission (CVT) to provide infinite ratios within its tuned range to deliver effortless shifting. A two-stage reduction gearbox is used to multiply the torque received from the CVT to provide sufficient traction to the tires. Power is transferred to the front differential via a propeller shaft. A shifting mechanism is installed for shifting between two-wheel-drive (2WD) and 4WD. Components are designed in SolidWorks and Fusion 360 is used for parametric iterations. The analysis is done on driveline components using Ansys and HyperWorks for material selection and to validate their durability. The performance of the driveline is mapped using MATLAB Simscape and Simulink models. This research paper aims to lay a foundation for future developments in the driveline used in a light ATV.
This paper investigates the application of torque weighting to vibration dose value. This is done as a means to enhance correlation of perceived drive comfort directly to driver pedal commands while rejecting uncorrelated inputs. Current industry standards for vehicle comfort are formulated and described by ISO2631, which is a culmination of research with single or multi-axis vibration of narrow or broadband excitation. The standard is capable of estimating passenger comfort to vibrations, however, it only accounts for reaction vibrations to controlled inputs and not perceived vibration request vs. response vibration. Metrics that account for torque inputs and the vibration response create actionable estimates of dosage due to driver torque requests without uncorrelated inputs. This reduces the need for additional accelerometers and special compensating algorithms when road or track testing. The use case for the proposed modified metric is during the powertrain calibration process. Specifically, it can be used to evaluate driver commanded torque transients that cause torque reversal(s) of the drivertrain, e.g., coast to drive or drive to coast, through pedal tip-in or tip-out, respectively. Two body on frame, solid rear axle, full-size trucks featuring a twin turbocharged gasoline direct injected engines each paired with a ten-speed automatic transmission and four-wheel drive selectable transfer case each were utilized in the investigation to collect test data. Road testing was performed on both vehicles instrumented with accelerometers, telemetry torque meters and CAN signal data. Vehicle NVH data in combination with standard and modified dose metrics acquired in various gear states, powertrain calibration configurations and vehicle loading states is presented. The utilization of transient event based torque weighting will be shown to improve correlation of subjective driver related NVH measurements to an objective quantity of dose value for the purposes of adjusting powertrain calibration.
Pass-by/exterior noise of earth moving machines (EMM) and forestry machines is becoming a focus at early product development stages. ISO 6395 (2) or EC/2000/14 (1) standards defines exterior noise test procedure for EMM. However, these standards do not provide insights for diagnosing any noise issues which may arise. The analysis challenges are posed by the moving machine and acoustic sources with respect to the stationary hemisphere target microphone on the ground and changing operating condition of sources as function of time. There is need to develop a seamless methodology to identify acoustic sources, quantify respective source strengths and rank partial contributions from each source to the total target microphone response in order to overcome the aforementioned challenges. This paper demonstrates use of time and frequency domain Acoustic Source Quantification (ASQ) combined with time domain overall sound pressure level computation to mimic operational test conditions which provides the ability to demonstrate partial contribution of each acoustic source during simulated exterior noise test run. The work was performed on a four-wheel drive Loader (4WDL) machine. This analysis approach provides quantified insights for the design team for overall machine noise improvements. To increase the value of such a method in the early design stage, an acoustic simulation model of a machine is developed, and a response analysis is demonstrated using the computed ASQ based results. The model is planned to be exercised for “what if” improvements based on contribution analysis. The physical modifications developed based on test results are implemented and tested for their effectiveness.
In this paper, in order to avoid the frequent switching of engine operating points and improve the fuel economy during driving, this paper proposes a control strategy for the 4-wheel drive (4WD) hybrid vehicle based on wavelet transform. First of all, the system configuration and the original control strategy of the 4WD hybrid vehicle were introduced and analyzed, which summarized the shortcomings of this control strategy. Then, based on the analyze of the original control strategy, the wavelet transform was used to overcome its weaknesses. By taking advantage over the superiority of the wavelet transform method in multi signal disposition, the demand power of vehicle was decomposed into the stable drive power and the instantaneous response power, which were distributed to engine and electric motor respectively. This process was carried out under different driving modes. The proposed control strategy not only ensured the dynamic property, but avoided the frequent switching of engine operating points by making the most of the fast-transient response of electric motor. Last but not least, in MATLAB/Simulink environment, the vehicle model and the control strategy model were built. Compared with the original control strategy, the simulation results showed that the proposed control strategy could reduce the range of engine operating points and make them more concentrated, which could effectively improve the working condition of engine. As a result, the proposed strategy improved the fuel economy, which verified the effectiveness of the control strategy based on wavelet transform.
A gray-box optimization procedure based on evolutionary algorithms for the initial design of a suspension concept for four wheel independently driven and steered vehicles is developed. With the presented optimization method, the energy consumption together with state of the art knowledge about the parametrization and design of vehicle suspension systems leads to an optimization setup closely to real world requirements while the vehicle’s topology is exploited. To this, the modelling presented in [1] is considered as a geometric suspension model. Furthermore, to take advantage of the potential of such vehicles, an autonomous closed-loop setup with integrated motion control is utilized. During the optimization, the chassis parameters with the most impact on energy consumption and driving dynamics, namely camber, caster, scrub radius and the steering axis inclination (SAI) depending on a varying caster angle and SAI in relation to the steering angle, will be focused. Therefore, the geometric arrangement of linkages, further considered as optimization parameters, substitutes certain modelling assumptions, leading to a realistic parametrization regarding mechanical design. The proposed chassis design procedure is divided into a five-stage sequence. After the model and controller initialization, roll and pitch centers are determined optimally in step two. In the following step, initial parameters of the suspension are determined in the design attitude with particle swarm optimization (PSO) and static maneuvers. Subsequently, the suspension characteristics, depending on the steering angles as well as the vehicle’s vertical dynamics, during the dynamic ISO double lane change is determined indirectly with genetic algorithms (GA) and the geometric parameters used as optimization variables. Finally, to verify the suspension also for future requirements, the resulting sets of parameters are checked with some unconventional driving maneuvers, which in particular make use of the larger steering angles.
All-wheel drive (AWD) and four-wheel drive (4WD) vehicles are becoming more prevalent in the market today. However, it is not well understood what the correct practice is when only one tire on the vehicle needs to be replaced. There are various recommendations and practices provided by tire dealers and car manufacturers to the consumer. The most common recommendation is to replace more than a single tire and match tread depths across all tires. The basis for this recommendation is the idea that tires with different tread depths will have a different number of revolutions per distance traveled due to differences in rolling radius. Mixing tires with different tread depths may cause extra wear or damage to the drivetrain components because, on a vehicle, the tires must rotate at different speeds to travel the same distance. In this study, the rolling radius of tires is measured on vehicle to understand the impact of tread depth, tire brand and model, and inflation pressure on the rolling radius. It was found that the rolling radius is not as sensitive to tread depth as it is to tire brand and model or even inflation pressure. Therefore, matching tread depths is not the most relevant criteria when replacing a single tire or tires in pairs. It is more important to match tire brand and model and maintain proper inflation pressure to ensure equal rolling radii across all tires.
Based on the traditional heavy commercial vehicle, hydraulic hub-motor drive vehicle (HHMDV) is equipped with a hydraulic hub-motor auxiliary drive system, which makes the vehicle change from the rear-wheel drive to the four-wheel drive to improve the traction performance on low-adhesion road. In the typical operating mode of the vehicle, the leakage of the hydraulic system increases because of the oil temperature rising, this makes the control precision of the hydraulic system drop. Therefore, a temperature compensation control strategy for the assist mode is proposed in this paper. According to the principle of flow continuity, considering the loss of the system and the expected wheel speed, the control strategy of multifactor target pump displacement based on temperature compensation is derived. The control strategy is verified by the co-simulation platform of MATLAB/Simulink and AMESim. The simulation results show that the temperature compensation control strategy compensates the flow loss of the hydraulic system, ensures the power output, and meets the requirement of the actual expected wheel speed. At the same time, the maximum grades of the vehicle under temperature compensation control strategy are all improved at different initial temperatures, and the maximum promotion ratio reaches 14.5%. The study in this paper improves the traction performance and promotes the environmental adaptability of HHMDV.
A procedure for the initial design of a suspension concept with four independently driven and steered wheels is developed, whereby, steering angles above conventional values are considered. To fully exploit the potential of such vehicles, an autonomous closed-loop setup with integrated motion control is utilized. The goal is to obtain statements for an optimal suspension design and parametrization maintaining a general approach, while underlying black-box control and the vehicle configuration remains exchangeable. The investigation of the influence of the chassis parameters, with crucial impact on energy consumption, comfort and driving dynamics, namely camber, caster, scrub radius and the steering axis inclination (SAI) depending on a varying caster angle and SAI in relation to the steering angle will be focused. For this sensitivity analysis, an explicit behavioral-oriented model of the suspension is created. This behavior is evaluated with the resulting driving dynamics, specified as the control error, comfort, regarding maximum acceleration on the passengers, and energy demand of the actuators. Scenarios presented are the ISO double lane change and driving a circle while accelerating. The results show clearly that the dependency of the vehicle behavior and the interaction of chassis and controller results in a dominant influence on the driving dynamics, while comfort only improves relatively. Potentials arise during dynamic maneuvers, while stationary driving is mostly influenced by the controller. With the presented design algorithm, different parametrizations obtained with additional maneuvers followed by a cross evaluation result in simulation determined near optimal suspension taking advantage of the exceptional suspension concept.
Almost all light trucks now are being manufactured with at least a driver side air bag and all will have dual air bags by 1998. The driving forces behind this feature are occupant safety, federal regulations, and competition in the industry. Along with the booming popularity of pickups and SUVs, they are commonly accessorized with a wide variety of products. Many accessories for four-wheel drives in particular are mounted on the front of the vehicle. These products include grille/brush guards, winches, snow plows, replacement bumpers, bicycle carriers, etc. Concerns have arisen over the compatibility of these accessories with the vehicle’s air bag system. The vehicle manufacturers are concerned because of their huge investment in design and crash test verification of the complete vehicle system and keen awareness of the federal regulations. The crushability of the front bumper and supporting structure are key elements in the system, so alterations to that area become logical concerns. The accessory manufacturers, dealers, and installers are concerned because the very core of their business could be at risk. The unknowns can range from fear of setting off an airbag while working on the vehicle to liability issues in an injury accident situation. In some cases, the installation of the product is contrary to recommendations from the vehicle manufacturer and may void the warranty. The ultimate customers (end users) are in a unique situation and are not being well served in some situations. Their dilemma stems from the conflict between what a manufacturer is willing to certify for sale and what the customer needs and expectations are. Their needs in vehicle equipment can vary widely from making a living to recreational lifestyle issues to simplify the desire to individualize. The precedent for front-mounted accessories is well established. The customers for both the vehicle and the equipment are there, so finding ways for them to coexist safely is beneficial to all.
The four-wheel drive electric sport utility vehicle (SUV) requires high dynamic performance, and the front and rear axles are matched with a high-power motor. High-power motors operate under low-speed and low-torque conditions, with low efficiency and large power loss. To reduce the power loss under low-speed and low-load conditions, a hybrid system of front and rear dual motors and dual hydraulic pumps/motors is designed. A simulation model of a four-wheel drive SUV electrohydraulic hybrid system is constructed. Aiming at the optimal energy consumption, a dynamic programming algorithm is adopted to establish the driving control rules of the vehicle. Constrained by the Economic Commission for Europe Regulation No.13 (ECE R13), a braking-force distribution strategy for the front and rear axles is formulated. On the premise of satisfying the braking safety, regenerative braking is preferred, and the braking energy is recovered to the greatest extent possible. The optimal efficiency curve of the motor is identified, and an energy-management strategy based on the optimal efficiency curve of the motor is established. The comprehensive efficiency of the dual motor for driving and braking is defined, and the energy-management strategy with the optimal comprehensive efficiency of the dual motor is established. Under the New European Driving Cycle (NEDC) condition, the equivalent energy consumption per 100 km for the two energy-management strategies is 13.2208 kWh/100 km and 13.1507 kWh/100 km. The latter has a higher overall efficiency and less power loss. Fuzzy-logic control with the accumulator pressure and its variation as the input and the threshold speed as the output is proposed, which improves the energy-management strategy with the optimal comprehensive efficiency of the dual motor. The results show that the equivalent energy consumption per 100 km for the improved strategy is 13.1481 kWh/100 km, and the vehicle energy consumption is reduced. The system design and control strategy are validated.
Powertrain electrification could be a key enabler for compliance with future exhaust emission standards and carbon dioxide (CO2) emissions limits or a customer facing product differentiator. The main objective of this study was to assess the potential of electrified propulsion systems in achieving a substantial reduction in CO2 emissions when applied to a representative full-size heavy-duty (HD) truck compared to the baseline configuration. A representative full-size HD four-wheel drive (4WD) truck of adjusted loaded vehicle weight (ALVW) 4082 kg or 9000 lbs with a 6.6 L diesel engine was simulated with various electrified drive configurations over the combined US FTP-72 (Federal Test Procedure) cycle and the Highway Fuel Economy Test (HWFET). Every hybrid vehicle configuration used in the study was designed using representative battery pack and electric drive components. Stop-start (S/S) functionality with a belt alternator starter (BAS) system provided a 2.5% benefit in CO2 emissions over the cycle compared to the baseline vehicle. Application of various electrified drive systems resulted in a total CO2 emissions benefit of 8.5% with a 48V P0 configuration to 25% with a high-voltage Series-Parallel hybrid over the test cycle. In addition to the CO2 emissions benefit, the impact of an electrified drive system on vehicle performance and utility was also assessed. This study provides an understanding of the potential benefits that can be achieved with application of various electrified propulsion systems to full-size HD trucks. The modeled CO2 emissions reduction and vehicle performance metrics have yet to be confirmed through hardware testing.
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