Dynamic characteristic analysis of distributed-compliant arm in vacuum suction device for scallop viscera separation

Abstract: The scallop is one of the major economic bivalves in China, whose adductor muscle is called shellfish. Shellfish are nutritious, delicious, and have many healthcare functions, edibleness and economic value. The automatic collection of adductor muscle usually includes 2 methods which are mechanical type separation and non-mechanical type separation. The mechanical separation uses mechanical device to separate adductor muscles and viscera compulsively, but this kind of method often causes lacerated hurt for adductor muscle, and low rate of finished products. The non-mechanical method realizes the separation of adductor muscle and viscera through adopting heat treatment, chemical reagent treatment, and ultrahigh pressure technology, etc. However, the non-mechanical separation destroys the nutrition component of adductor muscles because of the hot process on them. Therefore, the low-loss separation for adductor muscles of bay scallop and viscera is one of the key processes to realize the automatic collection. In order to reduce the high-loss of adductor muscles of scallop during automatic separation, this paper presents the suction separating device based on the distributed fully-compliant mechanism. The suction separating device is composed of suction tube and motivating mechanism. Due to the space limitation, it is difficult to use the traditional mechanism to realize the high-speed lift and the complicated location and posture of the suction tube, and so the motivating mechanism for suction tube with the compliant arm as the principal part can simplify the complication of mechanical structure observably. The motivating mechanism is based on the energy storage and deformation of the distributed fully-compliant arm to realize the control of locomotion and posture of the suction tube during separating process, so it is essential to analyze the dynamic characteristics for control. The pseudo-rigid-body model for the compliant arm is built, which makes the compliant mechanism equivalent to a multi-body system with underactuated joints. Based on the influence coefficient method, the dynamic model of the equivalent multi-body system for the compliant arm is established. According to the dynamic modeling, the second-order nonholonomic constraint equations are developed from the decomposition of the active joint and the equivalent passive joints, and then the acceleration expressions of passive joints and the input torque of active joint are obtained. The dynamic characteristic of the compliant arm is simulated and the prototype is tested, then the result proves that during the negative pressure adsorption, the connective part of compliant arm and suction tube can keep horizontal basically to ensure explosive power to viscera under negative pressure with the input angle of motor ≤56°; when the input angle ≥61°, the angle of the bottom of suction tube and horizontal direction that is between 25°-30°can satisfy the experiment data with compliant arm driving, which can make the target object break away from suction tube to end the adsorption process. The test results and simulation analysis are basically identical. Hence, based on the characteristics of the compliant mechanism by relying on elastic deformation itself to realize the transition of the locomotion and force with less even no kinematic pair in the mechanism, the motivating mechanism of suction tube proposed in this paper can simplify the mechanical structure and control system observably, and reduce the cost of equipment manufacture and energy consumption. The research on the separating device has very important application value for the realization of scallop automatic manufacture.