Requirements for designing robotic arms | china manipulator arm

Requirements for designing robotic arms | china manipulator arm

1. The arm should have large bearing capacity, good rigidity, and light weight

The rigidity of the arm directly affects the smoothness of the movement, the speed of the movement and the positioning accuracy when the arm grasps the workpiece. If the rigidity is poor, it will cause the bending deformation of the arm in the vertical plane and the torsional deformation of the inner side of the horizontal plane, the arm will vibrate, or the workpiece will be stuck and cannot work during the movement. For this reason, the arm generally adopts a guide rod with better rigidity to increase the rigidity of the arm, and the rigidity of each support and connecting piece must also have certain requirements to ensure that it can withstand the required driving force.

2. The movement speed of the arm should be appropriate and the inertia should be small

The movement speed of the manipulator is generally determined according to the production cycle requirements of the product, but it is not advisable to blindly pursue a high speed.

The arm moves from a stationary state to a normal speed for starting, and when it is reduced from a constant speed to a stop, it is for braking. The speed change process is a speed characteristic curve.

The arm's weight is light, and its start and stop are smooth.

3. The arm movements should be flexible

The structure of the arm must be compact and small to make the arm movement brisk and flexible. Installing rolling bearings or ball guide rails on the moving arm can also make the arm move lightly and smoothly. In addition, for a cantilevered manipulator, the arrangement of parts on the arm must be considered, which is to calculate the partial gravity moment of the weight when the arm moves the part against the center of rotation, lifting, and support. The partial gravity moment is very unfavorable to the arm movement. If the partial gravity moment is too large, it will cause the arm to vibrate, a sinking head phenomenon will also occur when lifting, and it will also affect the flexibility of the movement. In severe cases, the arm and the column will get stuck. Therefore, when designing the arm, try to make the center of gravity of the arm pass through the center of rotation or be as close as possible to the center of rotation to reduce the deflection moment. For a manipulator that operates both arms at the same time, the arrangement of the two arms should be as symmetric as possible to the center to achieve balance.

4. High position accuracy

In order to obtain a higher position accuracy of the manipulator, in addition to the advanced control method, the following problems should be paid attention to in the structure:

(1) The stiffness, partial gravitational moment, inertial force and cushioning effect of the manipulator directly affect the precise position of the arm.


(2) Add setting device and stroke detection mechanism.

(3) Reasonably choose the coordinate form of the manipulator. The position accuracy of the Cartesian coordinate manipulator is relatively high, its structure and movement are relatively simple, and the error is also small. The error caused by the rotary motion is the dimensional error during enlargement. When the position of the rotation angle is fixed, the longer the arm extends, the greater the error; the articulated manipulator has a complex structure, and the positioning of the hand is determined by the mutual rotation angle of each joint. The error is accumulated error, so the accuracy is poor, and its position accuracy is more difficult to guarantee.

5. Strong versatility, can adapt to a variety of operations; good craftsmanship, easy to maintain and adjust

The above requirements are sometimes contradictory. They have good rigidity and heavy load. The structure is often thick and the guide rod is large, which increases the weight of the arm. When the moment of inertia increases, the impact force is large, and the position accuracy is low. Therefore, when designing the arm, it is necessary to comprehensively consider various factors such as the grasping weight of the manipulator, the number of degrees of freedom, the working range, the movement speed, and the overall layout and working conditions of the manipulator to achieve accurate, reliable, flexible, compact structure and rigidity. Large, small weight, so as to ensure a certain position accuracy and adapt to rapid movements. In addition, for thermal processing manipulators, heat radiation must be considered. The arm must be longer to keep it away from the heat source, and it must be equipped with a cooling device. For dust-proof manipulators, dust-proof facilities should be installed.
china manipulator arm