Track Tension Research Articles

Mobility analysis of off-road vehicles: Benefits for development, procurement and operation

Nowadays the requirements on off-road vehicles are rising steadily. The ideal vehicle has to provide excellent off-road capability with low fuel consumption, offer a high customizability for each specific mission and, last but not least, it has to be easy to operate. To meet these demands, on the development side a lot of parameter studies have to be carried out. The customer has to compare offers from a multiplicity of suppliers to decide which vehicle fulfills the designated mission task best. And finally, the operator needs the best training on the vehicle to cope with all possible situations in off-road mobility. In response to these needs, the presented simulation program WinMaku was developed to offer a tool to facilitate development, procurement and operator training. Exemplary simulation results show, on the one hand, the influence of specific design parameters, e.g. tire size, engine power, torque characteristics, gear shifting, and engine working conditions, and on the other hand the (beneficial or adverse) effects of operational parameters like driving with maximum/partial engine load, gear selection, engine speed, tire inflation pressure or track tension, on mobility performance. Furthermore results of vehicle comparison analysis are presented. These types of analysis show comparisons of mobility performance of different vehicle types or vehicle concepts (e.g. wheel vs. track) in fulfilling a certain mission profile, characterized by passing a sequence of different soils with various inclines. Endowed with such capability, the presented simulation tool serves as a training tool for operators, provides a cost effective method to assess possible development steps, allows customers to run a pre-selection process prior to expensive and time-consuming field tests, and finally supports mission planning by providing data like expected fuel consumption or time needed to pass a certain mission profile.

고속 궤도차량의 동역학적 모델링 및 해석

This paper presents a dynamic model of a high mobility tracked vehicle composed of rigid bodies. Track is modeled as an extensible cable and the track tension between the sprocket and roller is calculated by the catenary equation. The ground force acting on a road wheel is calculated by the Bekker‘'s pressure-sinkage relationship using the segmented wheel model. System equations of motion and constraint acceleration equations are derived in the joint coordinate space using the velocity transformation method.

Study of Detracking Risks of Track Systems

Detracking is a complex phenomenon. It may occur to a tracked vehicle during turning manoeuvres, moving over obstacles, or operating on uneven surfaces. A fundamental study of detracking is lacking. As a first step in the study of this complex process, this paper focuses on the analysis of the necessary condition for detracking under steady state operations, such as in a steady turning manoeuvre on deformable terrain. The necessary condition for detracking is that the slacks in certain track segments are such that they enable the track to override the outside diameter of the sprocket or idler. Based on the analysis, detracking risk indicators have been developed for evaluating and comparing the risk for disengagement of track drive lugs or track guides from the sprocket or idler. These indicators have been applied to the evaluation of detracking risks of a segmented metal track system commonly used in current fighting vehicles and a rubber-band track system proposed for future combat vehicles. It has been found that track system configuration (including the location of the sprocket and idler), initial track tension, and braking or driving torque applied to the sprocket have significant influences on detracking. The track longitudinal stiffness and suspension stiffness have relatively insignificant effects on detracking.

An Investigation into the Effects of Initial Track Tension on Soft Ground Mobility of Tracked Vehicles Using an Advanced Computer Simulation Model

This paper describes the results of a detailed investigation into the effects of initial track tension (i.e. the tension in the track system when the vehicle is stationary on a level, hard surface) on soft ground mobility of tracked vehicles. The investigation was carried out using the latest version of an advanced computer simulation model, known as NTVPM, developed under the auspices of Vehicle Systems Development Corporation. The results show that the initial track tension has significant effects on the peak normal pressure and mean maximum pressure on the track-terrain interface, sinkage of the track, and the drawbar pull and tractive efficiency of a vehicle on unprepared terrain. The impact of initial track tension on tractive performance is however dependent upon vehicle design features, including suspension characteristics. This investigation demonstrates that the simulation model NTVPM can play a significant role in the detailed evaluation of the design of tracked vehicles from a traction perspective.

Evaluation of the effects of design features on tracked vehicle mobility using an advanced computer simulation model

On soft terrain, such as deep snow, track sinkage often exceeds vehicle ground clearance and the vehicle belly comes into contact with the terrain surface. This paper describes the results of a detailed investigation into the effects of design features, particularly the combined effects of initial track tension (i.e., the tension in the track system when the vehicle is stationary on a level, hard surface) and vehicle belly attitude (nose-up or nose-down), on soft ground mobility of tracked vehicles. The investigation was carried out using the latest version of an advanced computer simulation model, known as NTVPM, developed under the auspices of Vehicle Systems Development Corporation. The results show that the initial track tension has a significant effect on soft ground mobility, particularly when track sinkage is greater than vehicle ground clearance. When the vehicle belly is in contact with terrain surface, its attitude also has a notable effect on vehicle performance at low initial track tensions. However, its effect on mobility decreases with the increase in initial track tension. It is demonstrated that NTVPM is a useful and effective tool for design and performance evaluation of tracked vehicles from a traction perspective.

Track Tension Controller Design and Experimental Evaluation in Tracked Vehicles

Track tension is closely related to the maneuverability of tracked vehicles and the durability of their tracks and suspension systems. The tension needs to be maintained at an optimum level throughout the maneuver in order to minimize the excessive load on the tracks and to prevent track peeloff from the sprocket. In this paper, a track tension control system is developed for tracked vehicles which are subject to various maneuvering tasks. It consists of track tension estimator, track tension controller, and hydraulic unit. The tension around the idler and sprocket is estimated in real time, respectively. Using the estimated track tension and considering the highly nonlinear vehicle characteristics, a fuzzy logic controller is designed in order to control the track tension in the vehicles. The performance of the proposed tension control system is verified through simulation and experimental field tests.

A spatial motion analysis model of tracked vehicles with torsion bar type suspension

A spatial motion analysis model for high-mobility tracked vehicles was constructed for evaluation of ride performance, steerability, and stability on rough terrain. Ordinary high-mobility tracked vehicles are equipped with independent torsion bar type suspension system, which consists of road arms and road wheels. The road arm rotates about the axis of torsion bar, and rigidity of the torsion bar and cohesion of damper absorb sudden force change exerted by interaction with the ground. The motion of the road arms should be considered for the evaluation of off-road vehicle performance in numerical analysis model. In order to obtain equations of motion for the tracked vehicles, the equations of motion for the vehicle body and for the assembly of a road wheel and a road arm were constructed separately at first. Two sets of equations were reduced with the constraint equations, which the road arms are mechanically connected to the vehicle body. The equations of motion for the vehicle have been expressed with minimal set of variables of the same number as the degrees of freedom for the vehicle motion. We also included the effect of track tension in the equations without constructing equations of motion for the tracks. Numerical simulation based on the vehicle model and experiment of a scale model passing over a trapezoidal speed bump were performed in order to examine the numerical model. It was found that the numerical results reasonably predict the vehicle motion.

Advanced mobility in difficult terrain

The development and success of the Swedish Combat Vehicle CV90 has demonstrated the abilities of the author in the field of terramechanics related to tracked military vehicles. The honour of the Bekker–Reece–Radforth Award 2002 has been granted in recognition of these achievements made during the author's employment at Hägglunds Vehicle AB since 1975. Hägglunds Vehicle AB has been a producer of military vehicles since the late 1950s, although the first years concentrated on production only. From the early 1960s, Hägglunds developed a number of its own tracked vehicles, all of which were influenced by the mobility demands dictated by their intended use in severe terrain conditions, such as those found in Northern Scandinavia. This paper presents a brief history of the advancement of tracked vehicle technology at Hägglunds Vehicle AB. The concepts discussed include: ground pressure, the number of road-wheels, articulated steering, track tension, track attack angle, sinkage, belly effects, and the use of terramechanic simulation. The success of the CV90 demonstrates that the combination of practical experience, terrain knowledge, and terramechanic simulations can effect substantial improvements in vehicle mobility. Evaluation of the CV90 versus other modern combat vehicles of the same class has shown that the CV90 possesses considerably higher mobility and speed under severe terrain conditions. These two attributes provide CV90 with the ability to access terrain that similar vehicles cannot, thus giving the military user greater mobility options.

形状可変クローラの履帯張力調整機構を用いた階段自律移動(特殊移動ロボット1)

形状可変クローラの履帯張力調整機構を用いた階段自律移動(特殊移動ロボット1)

궤도차량의 동적 궤도장력 조절시스템에 대한 실험적 연구

Maintaining track tension in tracked vehicles minimizes the excessive load on the tracks and prevents the peal-off of tracks from the road-wheel, and adequately guarantees the stable and improved driving of the tracked vehicles. However, the track tension cannot be easily measured due to the limitation in the sensor technology, harsh environment, etc. In this study, the track tension is estimated in realtime from the measurable signals of tracked vehicles and controlled based on a fuzzy logic controller. The proposed control system is implemented on tracked vehicles and its performance is evaluated under various driving conditions.

Rut depth, soil compaction and rolling resistance when using bogie tracks

There are few studies of rolling resistance for bogie tracks on forestry machines. The aim of this study was to compare the effects of wheels and two types of bogie tracks on rut formation, cone index, and vehicle rolling resistance on some typical forest soils in Sweden. In an experiment, two types of tracks were put on a trailer with a bogie with hydraulic extension on the pulling bar giving the trailer repeatable travelling speed. Loads of 0 and 9.9 Mg were used on the trailer. The main results of this study are: Compared to rather wide and soft tires, tracks on the bogie reduced rut depth by up to 40% and cone index in the ruts by about 10%, although the tracks increased the mass on the trailer by 10–12%. The relative rolling resistance coefficient was not higher for tracks than for wheels. Further studies should be conducted to show the effect of track tension on rolling resistance and flotation and of the effects of tracks on heavy vehicles on subsoil compaction.

Development of a Multi-body Dynamics Simulation Tool for Tracked Vehicles (Part II, Application to Track Tension Controller Design)

Multi-body Dynamics simulation of tracked vehicles is very useful not only for the analysis of dynamic behaviors, but also for the performance evaluation of the chassis controllers. The track tension is closely related to the maneuverability of tracked vehicles and the durability of tracks and suspension systems. In order to minimize the excessive load on the tracks and to prevent the peal-off of tracks from the sprocket, the track tension needs to be maintained at the optimum level throughout the maneuver. In this paper, a co-simulation tool is developed such that the performance of the track tension control system cart be investigated for various maneuvering tasks. The MBD (multi-body dynamics) vehicle model for tracked vehicles is very complicated (189 bodies, 36 revolute joints, 152 bushing elements and 954 degrees of freedom) and cannot be easily implemented in commercial software. Besides, the track tension controller based on fuzzy logic can be easily constructed in the commercial control software. Therefore, co-simulation methodology is proposed so that the designed tension controller is interfaced into the MBD simulation software. The performance of the tension control system is verified through the proposed co simulation tool.

A Track-Wheel-Terrain Interaction Model for Dynamic Simulation of Tracked Vehicles

A mathematical model of track-wheel-terrain interaction is presented that supports the dynamic simulation of tracked vehicles. This model combines approximate and known constitutive laws for terrain response with a new representation for the track segment. The resulting track-wheel-terrain model allows the computation of the track tension and the normal and shear forces at the track-terrain interface as the track negotiates terrain of arbitrary profile. A key feature of this model is the uniform treatment of contact between the track and the roadwheels and the track and the terrain. Treating both contact problems in the same manner significantly simplifies the problem formulation and also reduces difficulties in computing points of track-wheel and track-terrain separation. The model takes the form of a two-point nonlinear boundary value problem that accounts for tension variations along the track (due to the non-uniformly distributed normal pressure and traction), track extensibility, and geometrically large (nonlinear) track deflections. Solutions are obtained using a finite element formulation. Both the model and the solution method are formulated for implementation within a multibody dynamics code for simulating full vehicles. Several examples illustrate the capabilities of the proposed model.

F-5-2-2 Development of a Multi-body Dynamics Simulation Tool for Tracked Vehicles, Part II : Application to Track Tension Controller Design

Multi-body Dynamics simulation of tracked vehicles is very useful not only for the analysis of dynamic behaviors, but also for the performance evaluation of the chassis controllers. The track tension is closely related to the maneuverability of tracked vehicles and the durability of tracks and suspension systems. In order to minimize the excessive load on the tracks and to prevent the peel-off of tracks from the sprocket, the track tension needs to be maintained at the optimum level throughout the maneuver. In this paper, a track tension control system is developed for tracked vehicles which are subject to various maneuvering tasks. It consists of track tension estimator, track tension controller and hydraulic servo unit. The track tension is estimated in real-time based on the idler assembly model. Using the estimated track tension and considering the highly nonlinear hydraulic units, a fuzzy logic controller is designed in order to control the track tension in tracked vehicles. The performance of the proposed tension control system is verified through the simulation of the Multi-body Dynamics simulation tool.

Modeling of 3-D Tracked Vehicle with Road Wheel Motion.

A three-dimensional tracked vehicle model including the effect of torsion bar type independent suspension system was constructed for simulation on rough terrain. The equations of motion for the vehicle body and a set of road wheel and arm were combined to reduce the number of variables for numerical efficiency. Vehicle motion is numerically obtained by solving the equations with minimal set of degrees of freedom. External forces to the vehicle equations are explained as an interaction relation between track and ground. In order to improve the model, track tension acting on the surface of road wheels was considered. Numerical calculation and scale model experiment were conducted to assess the validity of the mathematical model. It was found that the model exhibits good agreement with the experimental data.

Connectivity algorithm for an extended rubber-band track model

This study presents the formulation and implementation of the connectivity algorithm developed by the authors for the extended rubber-band track model. The vehicle model consists of a chassis, idlers, sprockets, support rollers, road arms, road wheels, and rotational spring-dampers-actuators. The extended rubber-band track model is a dynamic, spatial model; it takes into account the moment of inertia of the road wheel; it accounts for the friction at the road wheel-track interface; it models the suspension of each road arm by using rotational spring-damper-actuators; it models the track-terrain contact; a new method of computing the track tension is implemented. Several tests are performed for the tracked vehicle model in conjunction with the extended rubber-band track model that show the performance of the connectivity algorithm presented in this study.

Development of a track tension monitoring system in tracked vehicles on flat ground

The mobility of tracked vehicles is mainly influenced by the characteristics of the track assembly and by the interaction between tracks and soil. In particular, the track tension is closely related to the manoeuvrability of tracked vehicles and the durability of chassis components. In order to minimize the excessive load on the tracks and to prevent the peel-off of tracks from the sprocket, it is necessary to maintain the optimum track tension throughout the manoeuvre. However, the track tension cannot be easily measured owing to limitations in sensor technology, harsh environment, etc. In this paper an indirect track tension monitoring system is developed for tracked vehicles on flat ground based on idler assembly models, a geometric relation around the idler and the estimated tractive force using the extended Kalman filter technique. The performance of the tension monitoring system is verified with the results obtained from the multibody dynamics tool and an experimental set-up.

Track Tension Estimation in Tracked Vehicles Under Various Maneuvering Tasks

In this paper, track tension monitoring methodology is developed so that the track tension can be estimated under various maneuvering tasks such as longitudinal driving on sloping and/or rough roads, turning on flat or sloping roads, etc. The real-time information of the track tension is very important for tracked vehicles because the track tension is closely related to the maneuverability and the durability of tracked vehicles. In the case of longitudinal driving, a modified 3 DOF dynamics model is derived for tracked vehicles and is utilized for estimating the tractive force and track tension. In the case of turning, kinetic models for six road-wheels are obtained and used for calculating the track tension around the sprocket. This method does not require tuning of the turning resistance, which makes it difficult to estimate the track tension in turning. The estimation performance of the proposed methods is verified through simulations of the Multi-Body Dynamics tool. The simulation results demonstrate the effectiveness of the proposed method under various maneuvering tasks of tracked vehicles.

Study of the influence of vehicle parameters on tractive performance in deep snow

This paper describes an experimental study of tractive performance in deep snow, carried out with a new special skid steered tracked vehicle, developed by Bodin [1]. The vehicle design parameters studied include the influence of the ground clearance of the vehicle belly and the longitudinal location of the centre of gravity on tractive performance in deep snow, as well as the effect of initial track tension. The most important results from the test show that an increase in the ground clearance has a positive effect on the drawbar pull, originating from a greater increase in the thrust than in the track motion resistance and a slight decrease in the belly drag. Tests of the longitudinal location of the centre of gravity show that a location ahead of the midpoint of the track contact length is to be preferred. The drawbar pull increases with the centre of gravity moving forward. This is due to a reduced track motion resistance, a slight decrease in the belly drag and an almost constant vehicle thrust. The reason for the decreased track motion resistance and belly drag with the centre of gravity located ahead of the midpoint of the track contact length is a decreased vehicle trim angle.

A numerical method for dynamic analysis of tracked vehicles of high mobility

A numerical method is presented for the dynamic analysis of military tracked vehicles of high mobility. To compute the impulsive dynamic contact forces which occur when a vehicle passes on a ground obstacle, the track is modeled as the combination of elastic links interconected by pin joints. The mass of each track link, the elastic elongation of a track link between pin joints by the track tension, and the elastic spring effects on the upper and lower surfaces of each track link have been considered in the equations of motion. And the chassis, torsion bar arms, and road wheels of the vehicle are modeled as the rigid multibodies connected with kinematic constraints. The contact positions and the contact forces between the road wheels and track, and the ground and the the track are simultaneously computed with the solution of the equations of motions of the vehicle consisting of the multibodies. The iterative scheme for the solution of the multibody dynamics of the tracked vehicle is presented and the numerical simulations are conducted.