Skid-steered Vehicle Research Articles

1P1-J01 四輪スキッドステア車の左右車輪の速度比が走行軌跡に与える影響の実験的考察(車輪型/クローラ型移動ロボット)

This paper discusses experimental trajectories of a four-wheeled skid-steering vehicle. The trajectories are influenced by coefficient of friction, difference between right and left wheel speed, body speed, load distribution, inclination angle of a road, and so on. Analytical approach based on a dynamic robot model will show trajectory forms. However, it is difficult to get them due to complexity of calculation. We made it clear to show the trajectory of center positions of a robot on a floor while moving. Comparing experimental trajectories gives helpful information for tracing a given route.

Switching mode generation and optimal estimation with application to skid-steering

Skid-steered vehicles, by design, must skid in order to maneuver. The skidding causes the vehicle to behave discontinuously during a maneuver as well as introduces complications to the observation of the vehicle’s state, both of which affect a controller’s performance. This paper addresses estimation of contact state by applying switched system optimization to estimate skidding properties of the skid-steered vehicle.In order to treat the skid-steered vehicle as a switched system, the vehicle’s ground interaction is modeled using Coulomb friction, thereby partitioning the system dynamics into four distinct modes, one for each combination of the forward and back wheel pairs sticking or skidding. Thus, as the vehicle maneuvers, the system propagates over some mode sequence, transitioning between modes over some set of switching times. This paper presents second-order optimization algorithms for estimating these switching times. We emphasize the importance of the second-order algorithm because it exhibits quadratic convergence and because even for relatively simple examples, first-order methods fail to converge on time scales compatible with real-time operation. Furthermore, the paper presents a technique for estimating the mode sequence by optimizing a relaxation of the switched system.

325 スキッドステア車両の操縦性改善(車両操舵系の解析と制御,OS-16 運動と振動の制御,総合テーマ「伝統を,未来へ!」)

325 スキッドステア車両の操縦性改善(車両操舵系の解析と制御,OS-16 運動と振動の制御,総合テーマ「伝統を,未来へ!」)

614 スキッドステア車両型ロボットのスライディングモード制御(OS4-3 機械のダイナミクス3,オーガナイズドセッション:4)

614 スキッドステア車両型ロボットのスライディングモード制御(OS4-3 機械のダイナミクス3,オーガナイズドセッション:4)

Modeling and Simulation of an Autonomous Hybrid- Electric Military Vehicle

The U.S. Army TACOM-TARDEC developed and validated a high-fidelity six-degree-of-freedom model to use in a trade study for the development of a prototype autonomous vehicle. The model captures realistic dynamics of the six-wheeled, skid-steered vehicle along with the electrical, thermal, and mechanical response of a detailed series hybrid-electric power system with in-hub drive motors, lithium-ion battery, and generator linked to a diesel engine. These components were modeled and integrated via extensive power and energy component libraries developed for use with a high-fidelity software tool for dynamics modeling. Further, the vehicle model’s entire complement of components was integrated in a flexible configuration that allowed them to be readily adjusted or swapped out so the user could use the model to ascertain the relative effects of modifying the vehicle’s structural or power system components on specific vehicle evaluation criteria. Such criteria include the vehicle’s performance with high-speed stability, skid steering stability, body pitch/roll/dive/squat characteristics, braking capability, road/soft-soil traversal, and steering maneuverability.The model captures both the on- and off-road mobility for the vehicle via use of an extensive library of various terrains including hard surface, sand, sandy loam, clay soil, and snow. Further, detailed waypointbased path navigation routines automate the vehicle’s traversal over a number of user-selectable courses including some established military courses such as Churchville-B, Perryman 1, 3, and A, and Munson with user-defined vehicle velocities. The model functions as an executable file run independent of any proprietary or close-source software; the user utilizes a simplified interface to vary any of the variables associated with the vehicle’s geometry, power system, course and speed to navigate, and terrain type applied to the course. The graphical view for the vehicle traversing the selected terrain is shown with an open source 3D graphics tool. The model was validated by applying the specifications in the model for the prototype vehicle of the first-generation of autonomous six-wheeled skid-steered vehicle, simulating the model in maneuvers identical to those the prototype vehicle performed, and comparing the simulated and actual results; the data matched and the model was successfully validated.The vehicle model was designed primarily for the trade study for the design of a specific vehicle, but was created with sufficient flexibility and capability for modeling future vehicles as well. The interchangeability of the vehicle models’ components and environments allow a user to modify or replace the vehicle’s power system components, chassis masses, tires, transmission, duty cycles, courses to traverse, and many other aspects of the vehicle. Thus the user can essentially model any vehicle with similar types of components or structures and use that model to determine the impact of those elements upon many vehicle design considerations such as mass requirements, volume constraints, power system requirements, wheels design, suspension characteristics, and controls. Several new vehicle models are already being developed using this model’s flexibility and capability.

Comparing the steering performances of skid- and Ackermann-steered vehicles

Skid steering has advantages for military armoured vehicles because it gives greater internal hull volume and improved manoeuvrability. The steering performance of an 18t 6×6 skid-steered vehicle is analysed and compared with that of a similar Ackermann-steered vehicle. The basic properties of the double-differential mechanism used for steering most modern skid-steered vehicles are analysed. A tyre model is used that enables the force characteristics at combined slip to be established from the relatively small amount of pure slip data that are available for truck-sized tyres. A spreadsheet analysis is used for solving the equations of motion. This shows that the skid-steered vehicle is generally neutral to oversteer whereas the Ackermann-steered vehicle is understeer. The skid-steered vehicle is also shown to require more power when cornering because of the power required by the steering mechanism. This will increase the fuel consumption and reduce the range of the skid-steered vehicle.

539 スキッドステア車両の操舵制御

This paper discusses an application of sliding mode control theories to remote automatic operation of skid steer vehicle. Since it is very hard to control the angular velocity of the left-right wheel directly by an operator at middle or high speed, we have already proposed a model reference sliding control system by using a virtual steer angle demanded from the operator. However, it was assumed that the moment around the center of gravity of the vehicle could be generated as a control input. In this paper, a control subsystem to generate the desired moment is investigated. The unknown tire/road friction property is estimated, then a wheel velocity servo controller is designed in which the reference velocity is determined by the estimated tire/road friction property.

Behavior Analysis of Skid Steer Control Vehicles

This paper analyses the behaviour of skid-steering vehicles (SSV). The SSV vehicles direction can be changed by only applying wheel torque difference between the left and right wheels. A basic cornering characteristic of SSV was clarified by the transfer function of 2DOF model and a full vehicle model simulation. In addition, the relation between the change in turning radius to the acceleration or deceleration of SSV and the relation between input moment to lateral acceleration of SSV during cornering is clarified by a theory of quasi-steady state cornering. It was found that SSV shows over-steer characteristics under any situation, and some control is needed since it is difficult to drive SSV without control because the necessary input moment needed to have a steady turning has nonlinear characteristics with respect to the lateral acceleration.

An exploratory study of whole-body vibration exposure and dose while operating heavy equipment in the construction industry.

Whole-body vibration measurements were recorded for various types of heavy equipment used within the construction industry. The purpose of these measurements was to provide more information about the potential levels of whole-body vibration experienced by equipment operators in the construction industry, as well as to identify types of equipment warranting further research. In total, 67 pieces of equipment were tested from 14 different equipment types. Testing took place at various construction sites including corporate, public, and residential work projects. Measurements were made (following the 1997 International Standards Organization's 2631-1 whole-body vibration standards) for 20-minute testing periods using a Larson Davis HVM100 vibration monitor and a triaxial accelerometer. The mobile equipment tested was associated with greater levels of whole-body vibration than the stationary equipment. When whole-body vibration levels were compared to the International Standards Organization's 2631-1 standards, wheel loaders, off-road dump trucks, scrapers, skid steer vehicles, backhoes, bulldozers, crawler loaders, and concrete trowel vehicles exceeded the recommendations based on measured vibration dose values. Further research incorporating larger sample sizes and controlled testing conditions is required to better understand the levels of exposure experienced by operators as well as the amount to which seating, terrain, mobility, and vehicle structure might affect whole-body vibration.

Soft modelling and fuzzy logic control of wheeled skid-steer electric vehicles with steering prioritisation

The paper starts by discussing Ackermann-steering, and skid-steering as applied to wheeled vehicles. After a review of some of the previous techniques used to control land vehicles, the concept of `steering prioritisation' (SP) for skid-steer vehicles, which is the main focus of the work, is introduced. The overall contour skid-steer model (OCSM) is then developed, followed by the design of the fuzzy logic (FL) controllers for SP. Simulation results for a vehicle performing turns with and without SP are presented and it is demonstrated that improved performance is obtained with SP. Some data used in the simulations were obtained from a real vehicle demonstrator and details of this vehicle are given.