Harald Teufel

MPI Motion Simulator: Development and Analysis of a Novel Motion Simulator

This paper discusses the technical issues that were required to adapt a KUKA Robocoaster for use as a real-time motion simulator. Within this context, the paper addresses the physical modifications and the software control structure that were needed to have a flexible and safe experimental setup. It also addresses the delays and transfer function of the system. The paper is divided into two sections. The first section describes the control and safety structures of the MPI Motion Simulator. The second section shows measurements of latencies and frequency responses of the motion simulator. The results show that the frequency responses of the MPI Motion Simulator compare favorably with high-end Stewart Platforms, and therefore demonstrate the suitability of robot-based motion simulators for flight simulation.

MPI CyberMotion Simulator: implementation of a novel motion simulator to investigate multisensory path integration in three dimensions.

Path integration is a process in which self-motion is integrated over time to obtain an estimate of ones current position relative to a starting point 1. Humans can do path integration based exclusively on visual 2-3, auditory 4, or inertial cues 5. However, with multiple cues present, inertial cues - particularly kinaesthetic - seem to dominate 6-7. In the absence of vision, humans tend to overestimate short distances (<5 m) and turning angles (<30°), but underestimate longer ones 5. Movement through physical space therefore does not seem to be accurately represented by the brain. Extensive work has been done on evaluating path integration in the horizontal plane, but little is known about vertical movement (see 3 for virtual movement from vision alone). One reason for this is that traditional motion simulators have a small range of motion restricted mainly to the horizontal plane. Here we take advantage of a motion simulator 8-9 with a large range of motion to assess whether path integration is similar between horizontal and vertical planes. The relative contributions of inertial and visual cues for path navigation were also assessed. 16 observers sat upright in a seat mounted to the flange of a modified KUKA anthropomorphic robot arm. Sensory information was manipulated by providing visual (optic flow, limited lifetime star field), vestibular-kinaesthetic (passive self motion with eyes closed), or visual and vestibular-kinaesthetic motion cues. Movement trajectories in the horizontal, sagittal and frontal planes consisted of two segment lengths (1st: 0.4 m, 2nd: 1 m; ±0.24 m/s2 peak acceleration). The angle of the two segments was either 45° or 90°. Observers pointed back to their origin by moving an arrow that was superimposed on an avatar presented on the screen. Observers were more likely to underestimate angle size for movement in the horizontal plane compared to the vertical planes. In the frontal plane observers were more likely to overestimate angle size while there was no such bias in the sagittal plane. Finally, observers responded slower when answering based on vestibular-kinaesthetic information alone. Human path integration based on vestibular-kinaesthetic information alone thus takes longer than when visual information is present. That pointing is consistent with underestimating and overestimating the angle one has moved through in the horizontal and vertical planes respectively, suggests that the neural representation of self-motion through space is non-symmetrical which may relate to the fact that humans experience movement mostly within the horizontal plane.

Evidence for the contribution of S cones to the detection of flicker brightness and red–green

We were interested in the question of how cones contribute to the detection of brightness, red-green, and blue-yellow. The linear combination of cone signals contributing to flicker detection was determined by fitting a plane to 64 points (colors) of equal heterochromatic flicker brightness. A small S-cone contribution to flicker brightness of similar amplitude in all five subjects was identified. The ratio of L- to M-cone contribution was found to vary considerably among subjects (1.7-4.1). Chromatic detection thresholds were determined for small patches in the isoluminant plane defined by flicker brightness. These stimuli were presented at an eccentricity of 40 arc min. By using color naming at the detection threshold, one can attribute different segments of the resulting detection ellipses to different chromatic mechanisms. Linear approximation of these segments provided an estimate for the contribution of the different cone types to the detection of red-green and blue-yellow. The results are consistent with the hypothesis that S cones contribute to the red-green mechanism with the same sign as that of the contribution from L cones. The blue-yellow mechanism very probably subtracts S-cone contrast from luminance contrast. The detection ellipse can be mapped into a circle in cone difference space. The base of this canonical transformation is a set of three cone fundamentals that differs from previously published estimates. Projecting the circle onto the three cone difference axes produces sinusoidal changes within the respective excitations. We propose that simultaneous sinusoidal changes of equal increment in the three cone difference excitations generate stimuli differing by equal saliency.

Motion Scaling for High-Performance Driving Simulators

Advanced driving simulators aim at rendering the motion of a vehicle with maximum fidelity, which requires increased mechanical travel, size, and cost of the system. Motion cueing algorithms reduce the motion envelope by taking advantage of limitations in human motion perception, and the most commonly employed method is just to scale down the physical motion. However, little is known on the effects of motion scaling on motion perception and on actual driving performance. This paper presents the results of a European collaborative project, which explored different motion scale factors in a slalom driving task. Three state-of-the-art simulator systems were used, which were capable of generating displacements of several meters. The results of four comparable driving experiments, which were obtained with a total of 65 participants, indicate a preference for motion scale factors below 1, within a wide range of acceptable values (0.4-0.75). Very reduced or absent motion cues significantly degrade driving performance. Applications of this research are discussed for the design of motion systems and cueing algorithms for driving simulation.

Chromatic induction in humans: how are the cone signals combined to provide opponent processing?

We investigated the effect of 16 isoluminant chromatic surrounds on the perceived colour of an enclosed grey test-field at photopic (43 cd/m2) conditions. Stimuli were shown on a grey background identical to the test-field. Use of these stimuli implies that activations of receptoral (cS, cM, and cL) and postreceptoral (cM-cL, cS-(cM+cL)) mechanisms by surround colours are known quantitatively. This allows to predict shifts in colour of the test-field in terms of receptoral (adaptation) as well as postreceptoral (contrast) mechanisms assuming a standard two-stage model. Predictions are tested using matching and hue compensation procedures. Both procedures yield comparable results that are consistent with the assumption that postreceptoral mechanisms explain the observed shifts in perceived colour.

Learning System Dynamics: Transfer of Training in a Helicopter Hover Simulator

Transfer of training between the simulation of an inert and an agile helicopter dynamic was assessed involving a quasi-transfer design. The focus of this study was to test the ability of flight-naive subjects to successfully acquire and transfer the skills required to perform lateral sidestep hover maneuvers in a helicopter simulation. The experiments were performed using the MPI Motion Simulator with its ability to realize a highly realistic 1:1 motion representation of a simulated helicopter maneuver. As a result, the amount of training needed to stabilize either an agile or an inert helicopter dynamic did not differ. A clear positive transfer effect was found for the acquired skills from the agile to the inert dynamics but not from the inert to the agile dynamics.

The CableRobot simulator large scale motion platform based on cable robot technology

This paper introduces the CableRobot simulator, which was developed at the Max Planck Institute for Biological Cybernetics in cooperation with the Fraunhofer Institute for Manufacturing Engineering and Automation IPA. The simulator is a completely novel approach to the design of motion simulation platforms in so far as it uses cables and winches for actuation instead of rigid links known from hexapod simulators. This approach allows to reduce the actuated mass, scale up the workspace significantly, and provides great flexibility to switch between system configurations in which the robot can be operated. The simulator will be used for studies in the field of human perception research and virtual reality applications. The paper discusses some of the issues arising from the usage of cables and provides a system overview regarding kinematics and system dynamics as well as giving a brief introduction into possible application use cases.

Control of a lateral helicopter side-step maneuver on an anthropomorphic robot

Our society relies more and more on flight simulation for pilot training to enhance safety and reduce costs. But to meet the highest level of general technical requirements for simulators set forth by the FAA and EASA requires high-cost equipment. To make simulator use more accessible, reduced costs might be achieved with novel simulator designs and/or through research to improve the performance of existing designs. This report explores the use of such a novel design, based on an anthropomorphic robot arm to reproduce an experiment designed to evaluate flight simulator motion requirement for helicopter pilot training. Results compare promisingly well to those from a large, highperformance facility where the original work was performed.

Does jerk have to be considered in linear motion simulation

Perceptual thresholds for the detection of the direction of linear motion are important for motion simulation. There are situations in which a subject should not perceive the motion direction as, e.g., during repositioning of a simulator, but also opposite cases where a certain motion percept must intentionally be induced in the subject. The exact dependency of the perceptual thresholds on the time evolution of the presented motion profile is still an open question. Previous studies have found evidence for a sensitivity of the thresholds on the rate of change of acceleration, called jerk. In this study we investigate three motion profiles which differ in their jerk characteristics. We want to evaluate which profile can move people furthest in the horizontal plane in a given time without them noticing the direction. Our results suggest that a profile with a minimum peak jerk value should be chosen.

Towards Real-Time Aircraft Simulation with the MPI Motion Simulator

The paper describes the recent advancements gained on the MPI motion simulator project. The aim of this project is the use of an a nthropomorphic robot as actuation system for a motion platform intended for real time flight simulation. Almost all commercially available motion platforms rely on the so called St ewart platform, that is a 6-DOF platform that can bear high payloads and can achieve high accelerations. On the other hand an anthropomorphic manipulator offers a larger range of motion and higher dexterity, that let envisage this novel motion simulator as a viable an d superior alternative [1,2]. The paper addresses the use of a new inverse kinematics algor ithm capable of keeping joint velocities and accelerations within their limits. Preliminary experimental results performed using the proposed algorithm along with possible further improvements are discussed.