SLIP-Based Control of Bipedal Walking Based on Two-Level Control Strategy

SUMMARYIn this research, we propose a two-level control strategy for simultaneous gait generation and stable control of planar walking of the Assume The Robot Is A Sphere (ATRIAS) biped robot with unlocked torso, utilizing active spring-loaded inverted pendulum (ASLIP) as reference models. The upper level consists of an energy-regulating control calculated using the ASLIP model, producing reference ground reaction forces (GRFs) for the desired gait. In the lower level controller, PID force controllers for the motors ensure tracking of the reference GRFs for ATRIAS direct dynamics. Meanwhile, ATRIAS torso angle is controlled stably to make it able to follow a point mass template model. Advantages of the proposed control strategy include simplicity and efficiency. Simulation results using ATRIAS’s complete dynamic model show that the proposed two-level controller can reject initial condition disturbances while generating stable and steady walking motion.

A Matrix-Based Approach to Investigate the Geometrical Dependencies between Non-Driving-Related Tasks and Future Vehicle Concepts

Caused by the technology of automated driving the user is temporarily released from driving and can perform non-driving-related tasks (NDRTs), such as sleeping or working. The aim of this paper is to describe the geometrical interdependencies between NDRTs and different vehicle types, to be able to integrate them in the geometric package of the early phase of the vehicle conception. To address the objective a literature based study of existing approaches for vehicle conception and NDRT-studies was carried out. Additionally interviews with n=15 experts from the automotive conception department and a databased analysis of n=259 vehicles was conducted. Based on these investigations 91 geometrical characteristics for NDRTs and vehicle types werde determined and combined through a matrix-based approach. By analysing the approach highly connected characteristics such as the torso angle were identified and equations were set up to describe the relations. The approach can be used for different NDRTs such as relaxing and working and different vehicle types such as sporty cars or SUVs in order to integrate them into the package.

How does relaxing posture influence take-over performance in an automated vehicle?

The driver will not have to constantly monitor the vehicle while driving in a level-3 automation or at a higher level (SAE International, 2016), which enables the driver to conduct different activities and be out of the control loop. To achieve the goals of non-driving related tasks (NDRTs) rather than the driving task better, the driver may take other sitting positions, defined as “non-driving postures (NDPs)”. Different pos-tures represent different driver motoric states. This may result in different reactions to a take-over request (TOR). In this work, relaxing NDPs are built by manipulating the driver’s knee angle (133°) and torso an-gle (38°) via seat adjustments. Their take-over performances of each posture are evaluated. The torso angle is identified as a significant influencing factor: the reclined driver takes over more poorly, whereas a larger relaxing knee angle does not affect take-over performance if the heel is able to contact the pedal.

Automated identification of distinct events in an assembly process using tracking of body postures

An ergonomic assembly process is safer for operators and is more efficient in quality, time, cost and productivity. An assembly process is carried out in a series of distinct events. Ergonomic assessment of an assembly process therefore involves identification of the distinct events within the process and assessment of difficulty in carrying out each event, so that the process can be improved in an event-specific manner. So far, such assessment of assembly is carried out using video by identifying key frames manually. Manual identification of key frames consumes more time. To resolve this drawback, a novel approach has been proposed for tracking the body segments using electromagnetic trackers. It is done automatically in real time. Then, a data smoothening method is used for analysing automatically the tracked data to identify distinct events in an assembly process. An experiment in a laboratory setting is used in this study to test the following hypothesis: ‘An event is characterized by gross movements at its beginning and its end’. This hypothesis encapsulates the essence of the signature in postural data, which is used by the proposed method for identifying distinct events within an assembly; the tracked data were used to identify this signature automatically from the trackers and the tracked data set with a threshold of movement for each body segment; using this threshold, gross motions and thereby starts and ends of distinct events can be identified. The method of identifying events was based on a reach experiment; thus, the variation of torso angle was studied in this work. The result of the study indicates that this method can be applied easily in detecting events in an assembly. Performance of the proposed method is compared with the traditional method and it is observed that the proposed approach outperforms traditional method in terms of time and accuracy.

Kinematic Analysis on Chinese Outstanding Javelin Athlete Ma Qun’s Final Force

This paper mainly used the three dimensional photograph analysis method to analyze the best performance of Ma Qun and to acquire relevant kinematics parameters of his last exertion when throwing a javelin (mainly including the loss rate of body horizontal gravity speed, torso angle, right shoulder angle, length and time of the fourth step, the angle of javelin shooting, the posture angle, the stretch angle, attack angle, the shooting speed and height and so on),in order to analyze the recording in a more convenient way, we divide Ma Qun’s final exertion movement in his javelin throwing (by his right hand) into7 moments and 3 stages. During the javelin shooting stage, the initial javelin shooting speed of Ma Qun is 27.60 m/s, slower than the world’s excellent javelin athletes’ speed of 29.00m/s. The best angle of throwing javelin is about 32.00°, with the posture angle remain as 29.45°. And the javelin shooting angle of Ma Qun is 36.81° and his posture angle is 38.21°, both higher than the average index of the world’s excellent javelin athletes, casting a negative impact on his performance. After the comparison of relevant data between Ma Qun and excellent male javelin athletes all over the world, Ma Qun’s advantages and shortages have been found out, thus can help providing kinematics indicators and technical guidance for the training of Chinese athletes.