industrial robot

1390/09/12 23:25

نویسنده : شهرام قاسمی
ارسال شده در: الکترونیک ، روباتیک ،
Accuracy: How close does the robot get to the desired point? When the robot's program instruct the robot to move to a specified point, it does not actaully perform as per specified. The accuracy measrue such variance. That is, the distance between the specified position that a robot is trying to achieve (programming point), and the actual X, Y and Z resultant position of the robot end effector.

Repeatability: The ability of a robot to return repeatedly to a given position. It is the ability of a robotic system or mechanism to repeat the same motion or achieve the same position. Repeatablity is is a measure of the error or variability when repeatedly reaching for a single position. Repeatability is often smaller than accuracy.
    Robot Specification

Degree of Freedom (DOF) - Each joint or axis on the robot introduces a degree of freedom. Each DOF can be a slider, rotary, or other type of actuator. The number of DOF that a manipulator possesses thus is the number of independent ways in which a robot arm can move. An industrial robot typically have 5 or 6 degrees of freedom. 3 of the degrees of freedom allow positioning in 3D space (X, Y, Z), while the other 2 or 3 are used for orientation of the end effector (yaw, pitch and roll). 6 degrees of freedom are enough to allow the robot to reach all positions and orientations in 3D space. 5 DOF requires a restriction to 2D space, or else it limits orientations. 5 DOF robots are commonly used for handling tools such as arc welders.

Resolution: The smallest increment of motion or distance that can be detected or controlled by the robotic control system. It is a function of encoder pulses per revolution and drive (e.g. reduction gear) ratio. And it is dependent on the distance between the tool center point and the joint axis.

Robot Reach, Robot Envelope

Envelope: A three-dimensional shape that defines the boundaries that the robot manipulator can reach; also known as reach envelope.

    * Maximum envelope: the envelope that encompasses the maximum designed movements of all robot parts, including the end effector, workpiece and attachments.
    * Restricted envelope is that portion of the maximum envelope which a robot is restricted by limiting devices.
    * Operating
envelope: the restricted envelope that is used by the robot while performing its programmed motions.

Reach: The maximum horizontal distance from the center of the robot base to the end of its wrist.

Maximum Speed: A robot moving at full extension with all joints moving simultaneously in complimentary directions at full speed. The maximum speed is the theoretical values which does not consider under loading condition..

Payload: The maximum payload is the amount of weight carried by the robot manipulator at reduced speed while maintaining rated precision. Nominal payload is measured at maximum speed while maintaining rated preci-sion. These ratings are highly dependent on the size and shape of the payload due to variation in inertia.


Most industrial robots equipped with serial technology, where each axis is in line relative to the preceding one. The parallel robot on the other hand has three or more prismatic or rotary axes which function parallel to one another.

Examples of parallel robots are Tricept, Hexapod and Delta Robots. Both Tricept and hexapod robots use linear motors to control the position of the tool.

Tricept Robot: The tricept uses three legs in conjunction with a central pillar to hold the head rigidly in position and then has a standard wrist mounted on it to achieve the orientation.

Delta Robot: The Delta robot has three actuators which control all three translational degrees of freedom of the mobile platform. An additional linkage provides a rotational movement for the end-effector
The result of the parallel design is a robot that has increased stability and arm rigidity, with faster cycle times than serial technology. As such there is less flexing of the arms which results in high repeatability. In addition, With serial linked robots, the end-of-arm flexing errors are cumulative, whilst in a parallel link structure they are averaged. However, one disadvantage of parallel robots is they tend to have a relatively large footprint-to-workspace ratio, for example, the hexapod parallel robot, easily take up a sizable work area. The exception is the Tricept robot which requires less space. Another limitation of the parallel configuration is that it has a small range of motion due to the configuration of the axes when Compared to a serial link machine

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