Kinematic Modeling And Motion Control Algorithm Research For Multi-joint Arms Of Shotcrete Machine

The shotcreting machine is a type of machine that sprays concrete automatically tostrengthen slops or tunnel. As it saves energy and labor considerably, it is widely usedin the construction machine industry. However, the worker steers the different joints ofthe shotcrete manipulator used temporarily with several joysticks to let the nozzle dothe movements. They do their shotcrete tasks mainly based on experiences. It is hard forthem to guarantee a good quality of spraying. With the development of automaticcontrol technology, much research on shotcrete and shotcrete machines was done in thelast decades both in academic and engineering. This paper focuses its attention onrobotization of the shotcrete machine and studies its kinematics.Firstly, the kinematic model for shotcrete manipulator is established. Theshotcrete manipulator is hydraulic actuated and different joints are actuated by differenthydraulic components. This directly leads to complexity of kinematic model. So wesimplify this model and finally develop the kinematic relationship between actuatorspace, joint variable space and task space. The derived relationships construct a solidfoundation for the motion design and planning from actuator space to task space.The arm of shotcrete machine is made of7degrees of freedom, excluding thedegrees of freedom of spraying nozzle. It is very difficult to solve its inverse kinematicproblem as the manipulator has redundant degrees of freedom. A multi-objectiveoptimization inverse kinematic control algorithm based on gradient projection method isproposed in this paper to modify the joint motion range and velocity simultaneously.Two weighting factor are set to coordinate the two optimization objectives. Finally, themanipulator gets a good performance in motion safety and stability.A detail discussion on the imperfection of pseudo-inverse Jacobian technique ismade in this paper and a closed-loop scheme is proposed to eliminate the tracking errorsof the end-effector. This method guarantees a high accuracy of tracking performanceand it also can be used in motion control algorithm development for other manipulators.