Active gravity compensation test bed for a six-DOF free-flying robot
A novel active gravity compensation concept is proposed to simulate space on-orbit microgravity environments for free-flying robots on ground. Here, robots are suspended by active-controlled motion path tracking mechanisms through wires to compensate for gravitational forces. Based on the concept, an experimental test bed was designed and fabricated in laboratory to study on-ground kinematic and dynamic behaviors of a free-flying robot. The experimental fabrication contains an active horizontal motion tracking mechanism composed of primary and secondary active rotating arms. An multi-objective optimization method calculating the tension of the wires to minimize torques on robot joints is approved. The tension of the suspension wires is obtained through passive counterweights using pulley mechanisms. The kinematics and dynamics of a 6-DOF free-flying manipulator were calculated in MATLAB and simulated in MSC Adams under three working conditions: zero-gravity, gravity compensation and gravity. The lowest ratio of the torque compensation reached 80%. Agreements between numerical analyses and simulation results confirm the ability of this gravity compensation concept to simulate the kinematic and dynamic behaviors of free-flying manipulator in space.
A Dimension Reduced Ground Test Method of Dual-arm Space Robot for On-orbit Assembly
Dual-arm space robot used in on-orbit assembly is a free-floating space robot system. The key points of the prelaunch ground test are the realization of microgravity environment and the dynamics equivalent model of space robot. For a free-floating dual-arm space robot consists of one floating base and two six-DOF (degree of freedom) arms, we proposed an air bearing based ground microgravity test method. IMU (inertial measurement unit) and thrusters are mounted on the large base to monitor and counteract the disturbance of dual-arm motion to the base, respectively. A multipoint dynamic gravity compensation mechanism is designed to maintain the microgravity status of the robot in motion. The mechanism can avoid mutual interference of links. The dimension reduced three-DOF dynamics equivalent model in a plane is built from the six-DOF space arm. Finally, the method is validated by tracking the on-orbit trajectory of dual-arm unfolding and component assembly on an air bearing bed.
Suitability and water quality criteria of an open drainage municipal sewage water at Coimbatore, used for irrigation.
Sanganur canal is the major open drainage system which has intricate linkage with storm water supply, domestic sewage and industrial effluent disposal. Water samples from various stations were collected and analysed for physicochemical parameters to assess the water quality of the Sanganur canal system. The study revealed that physicochemical parameters like pH, EC, TDS, DO, BOD, COD exceeded the permissible limit, clearly indicating the need of proper treatment of waste water before discharge into the Noyyal river.