Research On Sensory System Of Space Manipulator And Joint Vibration Suppression

Chinese space station project was confirmed in 2005.According to the successful applications of SSRMS and JEMRMS,space manipulators are the most essential tools for extra-vehicular tasks.These tasks can be further divided into assembly and maintenance of ISS,load handling,detection of surface degradation,ORU replacement and EVA as-sistance,etc.In addition,space manipulators should function steadily with long-period life under harsh space environment,which includes high radiation and large temperature difference.The paper is supported by the research of XXX space manipulator.The paper will focus on the development of multi-sensory joint system,6-DOF acceleration sensor and its application in vibration suppression.High demands are crucial for space manipulator,which include longevity,high-reliability,sophisticated-task-execution,high-maintainability,etc.The paper is to develop the control system for multi-sensory joint,which is designed according to modularity and cold backup to improve the maintenance and reliability.Various and redundant sensors are utilized for different space tasks.Joint controllers are CPU and anti-fuse FPGA,which im-prove the reliability of the controller.The measurement range of the joint position sensor is enlarged by the fusion of redundancy digital Hall sensors without changing its resolu-tion.To compensated the output drift of torque sensor arising from time and temperature,the DA circuit is designated.A novel algorithm is proposed to compensate the output drift,which combines the faulty detection and drift compensation.Experimental results indi-cate that the modified torque sensor and the proposed algorithm are effectiveness.The motor current controller is fulfilled based on FPGA,which possesses small calculation delay and high reliability,etc.In order to overcome the conflict between the higher resolution and smaller phase delay in velocity estimation.The estimation method with adaptive sampling time is pro-posed.which can be adaptive for different velocity and desired relative measurement accuracy.In order to improve the development and debugging efficiency,A RTX-based real-time extension kernel is integrated with traditional Windows system on the same com-mercial PC.All real-time algorithms related to joint control can be migrated into the com-mercial PC.Contrast to Vxworks,the enhanced control system possesses the advantages of open characteristic,more friendly interface,better compatibility and augmentability,higher efficiency in the process of development and debugging.Experimental setup is established based on the enhanced control system to estimate parameters of joint dynamic model,test torque transmission characteristics of flexible joint,such as step response,fre-quency response and hysteresis.To suppress the vibration,a novel spatial geometric configuration is proposed ac-cording to the kinematic of rigid body moving freely.Multiple linear accelerometers are arranged based on the proposed geometric configuration to measure 6-DOF acceleration.The GDOP index and its extended indexes pGDOP,wGDOP are introduced from GPS to evaluate the proposed configuration.All indexes are ameliorated compared with the typical 6-DOF acceleration sensor.Redundant linear accelerometers improve the reliabil-ity of the proposed sensor.Error models are deduced to estimate and compensate sensor errors.Sensor errors are calibrated on the dedicated experimental setup.A novel decou-pling algorithms is proposed based on the extended Kalman filter,which includes errors and static bias compensation and noise suppression.Experimental results underline the effectiveness of the proposed sensor and errors compensation algorithm.Based on the proposed 6-DOF acceleration sensor,we investigate the vibration sup-pression by acceleration feedback.According to the successful application in rigid ma-nipulators,we analysis the application feasibility of acceleration feedback in flexible joint and prove its stability.By comparing acceleration feedback with other sensor feedback on the effect of vibration and disturbance suppression by the transfer function,the ad-vantages of the acceleration feedback are confirmed.Both simulation and experiments in position control indicate the acceleration feedback accelerates the attenuation of vibration and disturbance.In addition,impedance control experiments also show that acceleration feedback attenuates the contact oscillation at the instant of contact effectively,and shorten the effective contact time.