The design requirements of mechanical arm
1, the arm should be large carrying capacity, good rigidity, light weight
Arm rigidity directly affect the scraping of the artifacts of action, the movement speed and positioning accuracy. Such as poor rigidity will cause the arm of bending deformation in vertical plane and horizontal plane, medial to the torsional deformation arm will vibrate, or activity workpiece stuck unable to work. To this end, the arm is generally rigid good guide bar is used to increase the stiffness of the arm, each bearing, connecting rigidity also to have certain requirements, to ensure that can withstand the required driving force.
2, the rate of movement of the arm to appropriate, inertia is smaller
The rate of movement of the manipulator is generally according to the requirements of the product production rhythm to decide, but should not blindly pursue high speed.
Arm by stationary state at normal speed for the start, by the constant velocity to stop motionless for braking, the changing process of speed for the speed characteristic curve.
Arm light dead weight, the start and stop of smoothness.
3, arm movements are flexible
Small arm structure is compact, to do fast, flexible arm movement. Equipped with rolling bearing in motion arm or adopt ball guide can also make the arm movement is light, smooth. In addition, the manipulator of the cantilever, consider the parts in the arm to decorate, is to calculate the weight of the arm when moving parts on the rotary, lifting, support center of lay particular stress on torque. On torque is very bad, the arm movement on torque is too big, will cause the vibration of the arm, still happens when lifting a heavy head phenomenon, can also affect the movement of flexibility, serious when arms and columns will be stuck. When design the arm so try to make the arms of center of gravity by rotary center, or try to close to the rotary center and to reduce the torque. For manipulator arms at the same time operating, should make the two arms as far as possible to the layout of the symmetry in the center, in order to achieve the balance.
4, high location accuracy
Manipulator to get higher position precision, in addition to the adoption of advanced control method, in structure but also pay attention to the following questions:
(1) the stiffness of the manipulator, lay particular stress on torque, inertia force and the effect of buffer precision directly affects the position of the arm.
(2) added a positioning device and testing institutions.
(3) choose the coordinates of the manipulator. Rectangular coordinate manipulator position precision is higher, the structure and movement are simple, the error is small. And the error generated by the rotary motion is amplified when the size of the error, when the corner position must be the longer the arm stretched out, the greater the error; Hand joint manipulator because of its complex structure, the positioning by each joint Angle to determine each other, its error is accumulated error, so accuracy is poorer, its position will be more difficult to ensure accuracy.
5, strong commonality, can adapt to a variety of homework; Good manufacturability, convenient to maintenance
These several requirements, sometimes, often conflicting, good rigidity, big, structures are often bulky, guide bar, also increase the arm weight; The moment of inertia increases, the impact is big, position precision is low. When designing the arm, therefore, must according to the manipulator grasping the weight, the degrees of freedom, the scope of work, the movement speed and overall layout of the manipulator and the working conditions and other factors into account, the action in order to achieve accurate, reliable, flexible and compact structure, big stiffness, small weight, so as to guarantee position precision and adapt to the fast action. In addition, for hot working of the manipulator, also consider thermal radiation, arms are longer, and away from the heat source, and is equipped with cooling device is required. For dust homework manipulator to carry dust facilities.