Toward a dynamic analysis of bipedal robots inspired by human leg muscles

A walking bipedal robot by adding passive springs like mono and biarticular muscles which correspond to rectus femoris (RF), biceps femoris (BF), gastrocnemius (GAS) and tibialis anterior (TA) in human legs has been modeled in this paper. The stability of human-like leg walking can be achieved by adding these passive springs in the leg mechanism of bipedal robot. On the other hand, using these springs may inflict a fatigue during walking due to the additional work that can provide to the joints. The main objective of this paper is to analyze the total work of the robot during walking by proposing four cases of the preload of the springs at the equilibrium position. It’s found from this study that the case that has the most energy saving and ensure the comfortable walking to the robot is when the two muscles (GAS) and (TA) are not preloaded to support the total weight at the equilibrium position

Attitude determination and control system of Sharjah-sat-1

Sharjah-Sat-1 is the first CubeSat mission of the Sharjah Academy for Astronomy, Space Sciences, and Technology (SAASST), in collaboration with Istanbul Technical University Space Systems Design and Test Laboratory (ITU-SSDTL) and Sabanci University (SU). The 3U+ CubeSat's primary payload is an improved X-Ray detector (iXRD), with the objectives of detecting hard X-rays from very bright X-ray sources, as well as studying the solar coronal holes. The secondary payload is a dual-camera system for Earth imaging. A dual-camera system will be used to image the SAASST building with a size of about 100m. The iXRD requires an attitude accuracy of 1 degree or better. Its full width at half maximum is 4.26 degrees with a linear response for the square collimator used. Every 1-degree pointing error will lead to 23% information loss. The ADCS subsystem of Sharjah-Sat-1 has been carefully determined and selected to ensure the success of its sophisticated mission, considering the constraints on the CubeSat standards with regards to size, mass, and power, the operational requirements of the mission, and space environmental disturbances expected throughout the mission's lifetime. Those disturbances are mostly encountered at low altitudes, and Sharjah-Sat-1 is planned to have a Sun-synchronous orbit with an altitude of about 500 km, not exceeding 600km. The planned launch date of the mission is June 2022. The paper presents a discussion and evaluation of the ADCS system in detail and its importance in terms of the achievement of the Sharjah-Sat-1 scientific mission (both star/Sun imaging and Earth-imaging), the hardware and the software implemented for active control, and the various attitude determination and control modes for different sensors and actuators' configurations