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22/09/2015 893

DLR - ROboMObil

ROMO - The Robotic Electric Vehicle

The ROboMObil is an electro-mobility concept based on intelligent central control of four Wheel Robots, which integrate the drivetrain, brakes, steering and dampers. The integration of the vehicle dynamic actuation systems in the wheel vicinity is a relatively new development, and in recent years, several concepts and prototypes of this idea have emerged. Examples include the Michelin Active Wheel, Siemens VDO eCorner, MIT Wheel Robot , Volvo ACM and the Nissan Metamo system. In the case of Michelin, full size electrically powered vehicle prototypes (Heuliez Will and Venturi Volage) with the integrated wheel unit have been demonstrated. Some developments focussed on imparting the vehicle with the ability to rotate about its central axis or even to drive sideways, requiring extended steering angle ranges on all four wheels (e.g. Toyota Fine-X, Nissan Pivo II, MIT prototype with its Wheel Robot). This requirement of the extended steering angle on driven wheels necessitates the use of wheel-mounted drive systems and a certain degree of system integration into the wheel envelop. The ROboMObil makes use of the enhanced manoeuvrability offered by high steering angle range and in-wheel drive motors in the context of an autonomy-capable prototype vehicle.

Being a clean-sheet design, the ROMO explores the possibilities available for the future of mobility without the constraints applied by the modification of a conventional vehicle, making use of developments in intelligent systems from the field of robotics. With four mechanically independent modules, the ROMO allows the possibility of modifications to the chassis without affecting the powertrain, which is located completely in the two axle modules, with the actuators fully integrated within the Wheel Robots. The other modules are the body, which forms the structure of the vehicle and carries the cockpit, and the battery mounted beneath the cockpit floor. An intelligent robot control concept provides the ROMO with enhanced manoeuvrability.

The driver input can be given using a side-stick either from within the vehicle or via remote control. With the help of the integrated surround video cameras, the ROMO can be driven with various degrees of autonomy, from partial to fully autonomous. The modular design comprising the front and rear chassis modules, battery module and body module with cockpit makes ROMO an ideal technology platform for innovative vehicle dynamics control and energy management research, and a demonstrator for the fusion of robotics and electro-mobility. With energy efficiency becoming increasingly critical in all forms of future mobility, much attention has been paid to the energy supply of the ROMO. As well as employing state of the art Li-Ion battery technology, much effort is being put into modelling and estimation of the behaviour of the batteries.

The Wheel Robot

The Wheel Robot concept integrates all the vehicle dynamics actuators within the wheel envelop, resulting in fewer interconnections within the vehicle and allowing more flexible chassis layouts. Each Wheel Robot consists of a traction motor, a steering actuator, and a brake actuator. These four Wheel Robots are integrated in two axle modules, which house also the electrical distribution components.

Autonomous Driving

Autonomous driving is an essential research field of the ROboMObil project. Instead of adapting a conventional vehicle, our hardware has been built from the scratch for autonomous driving. Additionally, in contrast to active lidar or radar, which are mostly used for the environmental perception, the ROMO’s environment perception sensors are cameras.

Electrical Energy System

The main energy storage unit is a Lithium Ion Battery with sufficient capacity for a range of 100 km. It powers the traction motors. Two DC/DC converters connect the 340V high-voltage system with the 24V low voltage system, which supply the steering and braking actuators as well as the onboard computer systems. Advanced energy management is one of our research topics.

Human Machine Interface

The ROMO as a steer-by-wire system with three DoF allows and demands the design of new haptic input devices. A three DoF force-feedback joystick is used to command the vehicle movement direction compatibly, separately and unimanually to reduce the driver´s workload. Touchscreens provide i.a. a graphical user interface for user commands and a visualization of the environment generated out of the camera data.

System Architecture and Safety

The system architecture of the ROMO takes advantage of the design freedom provided by its development from a clean slate. A hierarchical approach allows systematic management of the complexity. The centralised control enables the use of higher performance global control strategies. Furthermore, safety is an important consideration in the development of the architecture.

Vehicle Dynamics Control

From a vehicle dynamics perspective the ROMO can be seen as a highly over-actuated system. This leads to opportunities and challenges concerning vehicle dynamics, which arise when designing the control algorithms for four individual steering actuators, four individual in-wheel motors, two hydraulic brake actuators and four semi-active dampers.

Technical Details

The ROboMObil is powered by four independantly controlled 16 kW electric motors with an overall peak torque of 640 Nm. An extended steering angle range allows the ROMO to rotate on spot and to move sideways. The following overview sums up the vehicles main dimensions and provides other interesting facts in addition to these key features.

X-By-Wire Test Rigs

The mechanical decoupling of the input device from the vehicle’s various actuators leads to challenging requirements on the control system performance, mechanical properties and safety-related behavior. Single-component-test rigs enable an isolated analysis of the vehicle’s subsystems to determine their physical behavior, control system performance and robustness, as well as long-term behavior.

Publications

The ROMO is a multidiscplinary test platform for various fields of research. The previous articles illustrate a short overview on the main scientific topics and the vehicle itself. Detailled information and results of research are consolidated in different publications and papers.

SOURCE: DLR

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