CyberMotion Simulator

MPI CyberMotion Simulator with cabin
open cabin
Sustained accelerations are usually simulated by use of motion cueing algorithms that involve washout filters. Using these algorithms, a fraction of the gravity vector generates the sensation of acceleration by an unperceived backward tilt of the cabin. A different solution to simulate sustained accelerations involves centrifugal force. If a subject is rotated continuously, the canal system adapts and the centrifugal force generates the perception of an ongoing acceleration. Both solutions require the subject to be seated in a closed cabin because the visual system would otherwise destroy the illusion.

Together with a local company (BEC, Reutlingen) the MPI developed a closed cabin for the MPS Cyber Motion Simulator. The cabin is equipped with a stereo projection and mounting possibilities for force feedback haptic devices like the Sensodrive steering wheel and the Wittenstein controls used for helicopter and flight simulation. To achieve continuous rotation around the base axis, the robot arm was modified by the manufacturer (KUKA robot AG, Germany). The robot was equipped with a different transmission and further mechanical modifications. Motor power and electrical control signals are transmitted to the robot by slip rings, an outer slip ring for power lines and an inner slip ring for high frequency signals. In its standard configuration, the cabin is attached to the robot flange from behind. In this configuration the subject faces outwards and it is possible to simulate constant deceleration by rotating the robot around its base axis. The 6 axes of the robot do not allow the possibility to place the subject facing inwards towards the base of the robot, so as to simulate constant acceleration. In order to achieve this possibility, the cabin was equipped with an actuated seventh axis. The C-shaped flange, along which the cabin axis can slide, provides the possibility to steer the robot into a position in which the cabin is attached to the robot flange from below. In this configuration, turning the last robot axis allows placing the subject towards the center of rotation that in turn grants the possibility to simulate a constant acceleration. The robot is equipped with its 6 axis controller and the 7th axis is equipped with a self developed separate controller. To achieve synchronized operation of the full 7 axis system, a combined control system was developed. This control system also monitors and supervises all safety devices and offers the possibility for manual and automated control of the MPI CyberMotion Simulator.

Stewart Motion Platform (MotionLab)

Reconstruction of the MotionLab
Foto: GEHIRN&GEIST/Manfred Zentsch
In the MotionLab we study the interplay between visual, auditory, vestibular and neuromuscular system. The center piece of the MotionLab is a hexapod Stewart platform (Cuesim) with six degrees of freedom. Mounted on the platform is a cabin with two interchangeable screens, a flat screen and a curved screen, both with a field of view of 86°×63°. The projector has a resolution of 1400×1050 with a refresh rate of 60 Hertz. Beneath the seat and foot plate are subwoofers which can be used to simulate high frequency vibrations in driving and flight simulators and mask the vibrations caused by the platform electric motors. The MotionLab was designed as a distributed system that is driven by multiple computers. Software control is based on an in-house development (xDevL) that can be used both with C++ and VirtoolsTM programs. The cabin has been equipped with 5 OptiTrack cameras (Natural Point Inc) that allow for tracking and capturing the operator’s body or limb motion.
The characteristics of the Stewart platform have been objectively measured with a standardized approach. It was found that the dynamic response of the platform is determined by the platform filters implemented by the manufacturer, the system time delay, and the noise characteristics of the actuators. These characteristics have been modeled and simulated on the SIMONA Research Simulator at Delft University of Technology. Experiments on the influence of these characteristics on human control behavior have shown that the limitations of the platform filters cause humans to rely predominantly on visual cues in a closed-loop target-following disturbance-rejection control task.
Furthermore, the MotionLab was used to study the effects of motion disturbances on the use of touch interfaces. When using a touch interface in a moving vehicle, the vehicle motion may induce involuntary limb motions which decrease manual control precision. The interference of motion disturbances on the use of touch interfaces was experimentally quantified. Participants performed a simple reach-and-touch task to interact with an iPad touch interface (Apple Inc) while being subjected to lateral and vertical motion disturbances. During the experiment, the motion disturbance, touch location, and trajectory of the hand were recorded. The goal of the study was to gain insight in the relationship between motion disturbances and touch errors.
The MotionLab is currently being upgraded with a state-of-the-art hexapod (Bosch Rexroth BV). Amongst other features, this hexapod has superior actuator technology, resulting in higher platform stiffness and increased motion smoothness.
Last updated: Tuesday, 20.01.2015