Effects of Turning Radius on Skid-Steered Wheeled Robot Power Consumption on Loose Soil

This research highlights the need for a new power model for skid-steered wheeled robots driving on loose soil and lays the groundwork to develop such a model. State-of-the-art power modeling assumes hard ground; under typical assumptions this predicts constant power consumption over a range of small turning radii where the inner wheels are rotating backwards. However, experimental results performed both in the field and in a controlled laboratory sandbox show that, on sand, power is not in fact constant with respect to turning radius. Power peaks by 20% in a newly identified range of turns where the inner wheels rotate backwards but are being dragged forward. This range of turning radii spans from half the rover width to R', the radius at which the inner wheel is not commanded to turn. Data shows higher motor torque and wheel sinkage in this range. To progress toward predicting the required power for a skid-steered wheeled robot to maneuver on loose soil, a preliminary version of a two-dimensional slip-sinkage model is proposed, along with a model of the force required to bulldoze the pile of sand that accumulates next to the wheels as it they are skidding. However, this is shown to be a less important factor contributing to the increased power in small-radius turns than the added inner wheel torque induced by dragging these wheels through the piles of sand they excavate by counter-rotation (in the identified range of turns). Finally, since a direct application of a power model is to design energy-efficient paths, time dependency of power consumption is also examined. Experiments show reduced rover angular velocity in sand around turning radii where the inner wheels are not rotated and this leads to the introduction to a new parameter to consider in path planning: angular slip

Operational criteria for battlefield vehicles

textModern military ground vehicles are no longer able to respond effectively to the rapidly changing mission requirements of modern military conflicts. Military vehicle architectures, which utilize passive suspension components and traditional drivetrain/steering systems, do not provide the operational flexibility to meet the demands of the operator. Advances in intelligent actuation technology allow for the development of a new vehicle architecture - the Intelligent Corner Vehicle (ICV). The ICV utilizes intelligent actuator technology to actively control the four degrees of freedom of each wheel of the vehicle - drive, camber, steering, and suspension. The utilization of intelligent actuation requires the characterization of the motions and behavior of the tire and the vehicle chassis in order to effectively apply the tire to the road surface - the development of vehicle performance criteria. A brief review of the state of wheeled military systems is presented. Many modern military vehicles were designed to improve protection at the expense of mobility - a process that has had negative effects on vehicle capability. An overview of the pneumatic tire used for wheeled vehicles is presented, highlighting the nonlinearities of tire behavior. The complexity of tire force generation drives the need for the application of intelligent actuation. Traditional actuation of wheel motion is presented along with a variety of current efforts to apply intelligent actuation to individual degrees of freedom of the tire. These efforts can be shown to improve vehicle performance, but intelligent actuation must be applied to all aspects of tire motion, requiring the use of the ICV architecture and the generation of performance criteria by which the complex motion of the vehicle may be evaluated. The Robotics Research Group has a history of developing and evaluating performance criteria for complex dynamic systems. and review of performance criteria developed for serial chain robotics is presented. These criteria address task independent actuator motion in addition to actuator ranges and limits, and their application to the ICV is discussed. A brief overview of several important concepts of classical vehicle dynamics are presented. The application of criteria derived from these concepts to the ICV architecture is discussed. This report presents the complexities of tire behavior and vehicle motion, the need for alternative architectures (the ICV), and a variety of performance criteria required to evaluate vehicle motion in real time. Criteria that are presented are summarized along with their definition and physical meaning. Future work for the development of the ICV involves the generation of a vehicle model for evaluating the application and range values of the presented criteria.Mechanical Engineerin

Characterizing Energy Usage of a Commercially Available Ground Robot: Method and Results

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106934/1/rob21507.pd

A study on automotive drivetrain transient response to ‘clutch abuse’ events

The optimal design of driveline components in passenger vehicles requires detailed knowledge of the effects that load case scenarios introduce into the system. In many cases the latter are difficult to obtain, since a large number of tested cases are required experimentally. Excessive torque loading often occurs during driveline ‘clutch abuse’ events, where the clutch is suddenly engaged and a transient power wave is transmitted across the driveline. This work details the development and validation of a numerical tool, which can be used to simulate such abuse scenarios. The scenario examined consists of a sudden clutch engagement in first gear in a stationary vehicle. The numerical model is validated against experimentally measured torque data, showing fairly good agreement. A set of parametric studies is also carried out using a numerical tool in order to determine the driveline parameters of interest, which affect the generated torque amplitudes

Design Issues and in Field Tests of the New Sustainable Tractor LOCOSTRA

first, in Italy, focusing on the agricultural application of the machine, in natural scenarios with different ground and vegetatio

An Experimental Method to Calculate Coefficient of Friction in Mecanum Wheel Rollers and Cost Analysis Using DFMA Techniques

Mecanum wheel is a special kind of omni-directional wheel which is designed for robot vehicles. The purpose of this thesis is to work on geometry and working of Mecanum wheel rollers and to conduct experiments on these rollers to find its values of coefficient of friction in different conditions. This thesis also includes the work conducted to formulate the equations which can be used to find different parameters of roller for its motion, kinematics, rolling, friction and overall impact with respect to the working of a robot. The work is tested in experiments and the values are compared with previous research values to validate the data. At the end, the derived components are tested in DFM (Design for Manufacturing) and DFA (Design for Assembly) to calculate all possible cost factors in manufacturing and assembly of rollers. This research is done with the support of a company called Helical Robots. Helical Robots is a leading manufacturer of Mecanum wheels and robots

DYNAMIC ANALYSIS OF VEHICLE SYSTEMS Development of a driving simulator Analysis and design of an automatic transmission for motor-scooters

In this work, two researches in the field of dynamic analysis of vehicle systems are presented. The first part of the thesis deals with the development of a driving simulator. This activity was carried out in the framework of a research project co-funded by the Italian Ministry of Education, Universities and Research (MIUR). It aimed at developing a driving simulator for the analysis of the driving style, in order to identify potentially dangerous conditions coming from a non proper interaction between driver, vehicle and environment, especially those related to low driver’s attention. As core part of the driving simulator, a vehicle simulation model, which reproduces the behaviour of the main vehicle systems, was developed. The simulator is made of a fixed driving platform, a single channel visual system and allows to acquire all driver’s inputs and vehicle motion signals. The system was involved in experimental campaigns which allowed the development of the driving style analysis techniques and demonstrated the reliability and the capability of the system. The second part of the thesis treats the dynamic analysis and design of a high efficiency automatic transmission for motor-scooters and was carried out in the framework of the Italian MUSS project funded by the Italian Ministry of Economic Development. Motor-scooters are currently almost always equipped with CVT transmission with rubber belt. This transmission can be very cheap to manufacture, it has good comfort performance but low mechanical efficiency. An alternative automatic transmission was analysed and different architectures were studied. The system is based on a discrete ratio gear box with mechanical control of the gear shit by means of centrifugal clutches and free wheels. A dynamic model of the transmission was developed and its behaviour was investigated by means of results of simulated manoeuvres, highlighting the positive and negative aspects of the system. Finally, a preliminary design was also carried out with reference to an application of the transmission in a hybrid powertrain

Design of a Mobile Robotic Platform with Variable Footprint

This thesis presents an in-depth investigation to determine the most suitable mobile base design for a powerful and dynamic robotic manipulator. It details the design process of such a mobile platform for use in an indoor human environment that is to carry a two-arm upper-body humanoid manipulator system. Through systematic dynamics analysis, it was determined that a variable footprint holonomic wheeled mobile platform is the design of choice for such an application. Determining functional requirements and evaluating design options is performed for the platform’s general configuration, geometry, locomotion system, suspension, and propulsion, with a particularly in-depth evaluation of the problem of overcoming small steps. Other aspects such as processing, sensing and the power system are dealt with sufficiently to ensure the feasibility of the overall proposed design. The control of the platform is limited to that necessary to determine the appropriate mechanical components. Simulations are performed to investigate design problems and verify performance. A basic CAD model of the system is included for better design visualization. The research carried out in this thesis was performed in cooperation with the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt)’s Robotics and Mechatronics Institute (DLR RM). The DLR RM is currently utilizing the findings of this research to finish the development of the platform with a target completion date of May 2008

Standardization for intelligent detection and autonomous operation of non-structured hardware, and its application on railcar brake release operation

textThis thesis introduces a standard framework for evaluating and planning for desired autonomous (or semi-autonomous) operations, then applies the framework, in detail, to the task of automating emergency brake release before rail-car decoupling. A significant hurdle to be accounted for is the lack of standardization of much of the hardware of interest in industry. Non-standardized rail car components must be formally structured as fully as possible to improve the reliability of the robotic automation. This brake release task requires either pushing or pulling a “bleed rod” that protrudes from the side of each rail car. The requirements for each step of the evaluation and planning process will be laid out in this thesis, as an example of how it should be applied to future automation tasks.Mechanical Engineerin