Design And Research Of Compound Drive Flexible Underactuated Manipulator

In the traditional light industry,agriculture and food industries,as well as the distribution and packaging processes of emerging electricity businesses,due to the large size change,complex shape(object shape effect)and soft and hard crisp(physical property effect)of the captured objects,the handling of the objects is mostly done by manpower,and a universal manipulator is urgently needed to meet the object grabbing requirements in these scenes.Based on the research of underactuated manipulators at home and abroad,this paper proposes a new type of flexible underactuated manipulator driven by electricity and gas.The manipulator has better adaptability of size and shape and higher operating efficiency.This paper first introduces the principle analysis and structural design of the manipulator,which consists of a variable palm and three rigid-flexible coupling skeleton fingers.The variable palm structure can realize stepless angular indexing of the finger roots of two groups of fingers with maximum indexing of 60 degrees in the forward and reverse directions along the vertical axis respectively,and can meet the adaptive grabbing of the shapes of a cylinder,a cuboid,an elliptic cylinder and the like;The closed-loop stepping motor drives the connecting rod mechanism to realize the 90-degree accurate rotation of the three finger roots along the horizontal axis,thereby not only meeting the adaptability to the size change of the object,but also adjusting the direction and size of the contact force.Rigid-flexible coupling skeleton fingers are series hinge skeleton APA type underactuated fingers.The pen-shaped inner guide cylinder directly drives the fingertip joint from the finger root joint.At the same time,it overcomes the resistance of large and small torsion springs on the series hinge mandrel and realizes the functions of pinching and enveloping grabbing.The fingers driven by pneumatic have the characteristics of structural flexibility,driving flexibility and the like,which can simplify the transmission chain and improve the clamping efficiency.At the same time,in order to study the grasping performance of the manipulator,the kinematics analysis of rigid-flexible coupling skeleton fingers is carried out,and the real-time coordinates of each point on the manipulator are expressed by D-H matrix method.In addition,static analysis is carried out on the three working states of the manipulator,i.e.the three fingers grabbing the cylinder in a uniform state,grabbing the cuboid in a grabbing state and grabbing the elliptic cylinder in an intermediate state.The analysis results show that the manipulator can accurately control the size and position of contact force on the basis of satisfying the shape and size of the object.Then,the Fmincon function is used to optimize the installation center distance of the manipulator fingers,Hooke's coefficient and pretightening angle of large and small torsion springs,taking the minimum pressure of the finger driving cylinder as the optimization objective when grasping the common beverage cans with the largest diameter.The influence of the rotation angle of the finger root joint and the size change of the object to be grasped on the contact force and the height of the contact point is discussed in detail.The virtual prototype model of the manipulator is established in ADAMS software.Static simulation is carried out on the objects to be grasped by cylinder,cuboid and elliptic cylinder respectively.The change of the contact force between the finger and the object is obtained.The error between the theoretical calculation value and the simulation result is only 1~2%.The conclusion verifies the correctness of the mathematical model and the calculation formula,and discusses the causes of the error.After the structural design of the manipulator is completed,in order to meet the requirements of contact force control,a finger drive circuit based on precise control of pneumatic high-speed on-off valve pressure is designed,and a manipulator control system based on PLC is designed.The corresponding control program is written to realize the coordinated control of the rotation angle of the stepping motor and the thrust of the finger-driven cylinder.The touch screen is used as the display and input module,and the reliable grasping of various different objects can be realized by manually inputting the calculated control parameters.Finally,a prototype of the manipulator and its control system are made.Through physical tests,the precise control effect of the pressure of the finger-driven cylinder is verified,and the grasping adaptive experiment of the manipulator is completed.It is verified that the manipulator can reliably grasp objects with large size changes and complex shapes.