Browse Topic: Slip
ABSTRACT A new integrated testing system for the validation of stochastic vehicle-snow interaction models is presented in this paper. The testing system consists of an instrumented test vehicle, vehicle-mounted laser profilometer and a snow micropenetrometer. The test vehicle is equipped on each tire with a set of 6-axis wheel transducers, and a GPS-based data logger tracks vehicle motion. Data is also simultaneously acquired from the sensors from the test vehicle’s Electronic Stability Program. The test vehicle provides measurements that include three forces and moments at each wheel center, vehicle body slip angle, speed, acceleration, yaw rate, roll, and pitch. The profilometer has a 3-D scanning laser and an Inertial Measurement Unit to compensate for vehicle motion. Depth of snow cover, profile of snow surface and wheel sinkage can be obtained from the profilometer. The snow micropenetrometer measures the strength of the snow cover before and after vehicle traversal. Preliminary
ABSTRACT When building simulation models of military vehicles for mobility analysis over deformable terrain, the powertrain details are often ignored. This is of interest for electric and hybrid-electric vehicles where the maximum torque is produced at low speeds. It is easy to end up with the drive wheels spinning and reducing traction and eventually the vehicle digging itself down in the soil. This paper reveals improvements to mobility results using Traction Control Systems for both wheeled and tracked vehicles. Simulations are performed on hard ground and two types of deformable soil, Lethe sand and snow. For each soft soil, simulations have been performed with a simple terramechanics model (ST) based on Bekker-Wong models and complex terramechanics (CT) using the EDEM discrete element soil model which Pratt & Miller Engineering (PME) has been instrumental in developing. To model the traction control system a PD controller is used that tries to limit the slip velocity at low speed
Abstract This paper presents the development of a transmission-in-the-loop (TiL) experimentation system. In this TiL experimental setup, the input side of the transmission is controlled by a dynamometer emulating the engine, while the output sides of the transmission are controlled by two dynamometers emulating the wheels and vehicle. The models emulating these vehicle components are required to possess sufficient fidelity to simulate engine torque pulse (ETP) and wheel slip dynamics while being computationally efficient to run in real-time. While complex engine and tire models exist in the literature that accurately capture these dynamics, they are often too numerically stiff for real-time simulation. This paper presents the system level details of such a TiL setup, and the modeling concepts for the development of high fidelity real-time models of the engine and tire dynamics for use in this experiment. Parameters of the engine model are identified using experimental data. Vehicle
Vehicle chassis design can take great advantage from a virtual design approach, as it helps tackle the complexity of modern machines, bringing benefits in performance, development cost, and lead-time. For specific applications such as construction or defense vehicles, the simulation design chain may lack significant input model bricks due to the physical limitations of existing test equipment which limit their ability to characterize the large components and extreme loading conditions (high loads, large torques, extreme slip angles. etc.). Michelin SIMIX proposes / develops an innovative solution to fill the gap by combining physical real world measured data with virtual measurements, allowing the creation of digital models relevant to the full usage perimeter
The pursuit of maintaining a zero-sideslip angle has long driven the development of four-wheel-steering (4WS) technology, enhancing vehicle directional performance, as supported by extensive studies. However, strict adherence to this principle often leads to excessive understeer characteristics before tire saturation limits are reached, resulting in counter-intuitive and uncomfortable steering maneuvers during turns with variable speeds. This research delves into the phenomenon encountered when a 4WS-equipped vehicle enters a curved path while simultaneously decelerating, necessitating a reduction in steering input to adapt to the increasing road curvature. To address this challenge, this paper presents a novel method for dynamically regulating the steady-state yaw rate of 4WS vehicles. This regulation aims to decrease the vehicle's sideslip angle and provide controlled understeer within predetermined limits. As a result, the vehicle can maintain a zero-sideslip angle during turns with
This SAE Recommended Practice is intended as the definition of a standard test, which may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 friction test is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluid combinations. The specific purpose of this document is to define a µPVT test for the evaluation of the variation of wet friction system low speed slip characteristics as a function of speed, temperature, and pressure. This procedure is intended as a suggested method for both suppliers and end users. The only variables selected by the supplier or user of the friction system are: Friction material Fluid Reaction plates Oil flow (optional) These four variables must be clearly identified when reporting the results of this test. If any of the test parameters or system hardware as described in this document are changed
This study examines the impact of slip in aero-thermal conditions of supercooled large droplets (SLD) produced in an Icing Wind Tunnel (IWT) on the ice accretion characteristics. The study identifies potential biases in the SLD model development based on IWT data and numerical predictions that assume the SLD to be in aerothermal equilibrium with the IWT airflow. To obtain realistic temperature and velocity data for each droplet size class in the test section of the Braunschweig Icing Wind Tunnel (BIWT), a Lagrangian droplet tracking solver was used within a Monte Carlo framework. Results showed that SLDs experience considerable slips in velocity and temperature due to their higher inertia and short residence time in the Braunschweig IWT. Large droplets were found to be warmer and slower than the flow in the test section, with larger droplets experiencing larger aerothermal slips. To examine the impact of these slips, numerical ice accretion simulations were performed on a NACA 0012
Upcoming, stricter diesel exhaust emissions standards will likely require aftertreatment architectures with multiple diesel exhaust fluid (DEF) introduction locations. Managing NH3 slip with technologies such as an ammonia slip catalyst (ASC) will continue to be critical in these future aftertreatment systems. In this study, we evaluate the impact of SO2 exposure on a state-of-the-art commercially available ASC. SO2 is co-fed at 0.5 or 3 ppmv to either approximate or accelerate a real-world exhaust SO2 impact. ASC performance during sulfur co-feeding is measured under a wide variety of simulated real-world conditions. Results indicate that the loss of NO conversion during SCR is dependent on the cumulative SO2 exposure, regardless of the inlet SO2 concentration. Meanwhile, N2O formation under SCR conditions is nonlinearly affected by SO2 exposure, with formation increasing during 0.5 ppmv SO2 exposure but decreasing in the presence of 3 ppmv SO2. TPO experiments reveal the formation of
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