Application Potential of Wheeled Mobile Driving Simulators

Mobile omnidirectional platform for highly dynamic tire-bound driving simulation

A driving simulator (DS) simulates different traffic situations to the test person within a limited space, which in reality extend over a larger space.

A simulative and prototypical development environment for omnidirectional motion concepts of a DS platform was created within the framework of a project funded by the German National Academic Foundation and the German Research Foundation (DFG). The research platform MORPHEUS (Mobile omnidirectional platform for highly dynamic, tire-bound driving simulation), which was developed within this course, was put into operation for the first time at FZD on 4 February 2015. The basic feasibility of the new concept was proven in simulations and tests based on objectively measurable criteria.

Based on the previous research results, the MORPHEUS project was continued under the name MORPHEUS 2.0. The development of a demonstrator suitable for test person studies is currently ongoing. The aim of the project is to validate that the DS also proves itself in subject studies and that at least the same or even higher immersion quality compared to the current state of the art is achieved at significantly reduced costs. For this purpose, a platform enlarged by a factor of two compared to the first prototype, including driver cabin and simulation environment is developed and set up at FZD. Further steps are the investigation of suitable control concepts for the realistic representation of accelerations as well as the development of an integral safety concept for the safe execution of test person studies.

Design Concept for MORPHEUS 2.0

The planned set up consists of a cabin in which the mock up and its components for the drivers inputs (gas and brake pedal, steering wheel) are placed. The driver wears a head mounted display (HTC Vive Pro) for the visualization of the simulated scene. The mockup is based on three linear actuators which are used to represent high frequency vibrations (e.g. induced by a combustion engine). The entire cabin is mounted on a hexapod with six degrees of freedom, which can represent acceleration forces by tilting the cabin. This setup is carried by a 3-wheeled platform, which also features a high-voltage accumulator and other components such as computing units and control cabinets. The wheel units are electrically driven and steered and have unlimited steering angles so that the WMDS can move quickly in any spatial direction.

Since the WMDS is intended to be mobile and operated on flexible free spaces, it requires a safety concept that can also be used on a mobile basis and protects against both internal faults and potential collision objects from the environment. Therefore, we are developing LIDAR sensor based safety functions: a collision protection and a position determination with artificial landmarks. MORPHEUS is to be operated at the August Euler Airfield in Griesheim. Since Until its completion, the virtual prototype already enables many simulations in the target environment for the development of the control concepts and safety functions.

Collision protection and a position determination with artificial landmarks

While the wheel based motion platform is still under construction, the upper part with hexapod and driver's cabin is already in use for driving simulation experiments in our FZD workshop.

The research on this topic is supported by international experts from the field of driving simulation in form of a research committee. The project is funded by the Federal Ministry of Education and Research (BMBF) within the framework of the funding measure “Validation of the technological and social innovation potential of scientific research – VIP+”.

Fields of Research:

  • Development of control algorithms and evaluation
  • Integral safety concept and test procedures

Responsible employees: Torben Albrecht, Xing Chen, Melina Lutwitzi

Unlike the motion control in the field of autonomous driving and mobile robots, the development of the control system for wheeled-based driving simulators has special requirements. As the driving simulator is designed to provide the proband with a high fidelity simulation of driving experience, its control system is based on high order acceleration, and in addition to meeting the basic requirements of stability and robustness, it also takes into account the special characteristics of the human vestibular system in terms of motion perception.

The proband's motion is formed by the low-frequency motion of the hexapod superimposed on the high-frequency motion of the platform. After determining the hexapod's control strategy through motion-cueing algorithm, the non-linear nature of the motor and tire first posed challenges to the development of the motion platform control system. Due to the high dynamic motion, the real-time estimation and correction of tire forces becomes the key research topic in the acceleration control.

In this research, a layered control system is constructed for the purposes of force distribution and correction, robust control, and task execution respectively. The optimization and coordination of algorithms in each layer are ongoing to improve overall control system performance.

This topic is researched by Xing Chen (opens in new tab)

The decision for a tire-based motion platform for driving simulators transforms a previously physically guided system into an automated vehicle with a theoretically infinite range of motion. Due to the intention to operate a WMDS on flexible workspaces, limiting the range of motion or preventing collisions with mechanical mechanisms is not an option. It must nevertheless be ensured that this vehicle in motion neither is hazardous for the test persons within, nor for persons in its operative environment. As a result, keeping the WMDS in a safe state of motion and avoiding collisions at all times is a major safety goal. The research in this field concerns the development and validation of designated safety functions to safeguard a WMDS within a mobile operational concept. This requires a safe and profound definition of requirements on the function while avoiding interference with the driving simulation itself. Environment sensing systems are applied in the scope of the research and novel safety functions for collision avoidance and workspace compliance are implemented according to the predefined requirements. A challenge is to achieve fail-safety of the respective functions and to validate their protecting effect, which requires testing strategies under worst-case conditions.

This topic is researched by Melina Lutwitzi.