The purpose of this article is to make users know the difference between xArm5, xArm6, and xArm7.
2) Motion Characteristics
Compared with xArm6 and xArm7, the motion characteristics of xArm5 are quite special.
Motion Characteristics of the xArm5
● Cartesian space
The movement of xArm5 is relatively special. Due to the structural limitation, the actual flexible degrees of freedom of linear and circular motions in Cartesian space is 4, which is [x, y, z, yaw], similar to a SCARA manipulator with four degrees of freedom. Before starting Cartesian control, it is necessary to ensure that the end flange surface of xArm5 and the base are completely parallel. If mounted on horizontal plane, the roll and pitch should be [± 180 degrees, 0 degrees], otherwise the trajectory is likely to have no solution.
● Joint space
In joint space, the robotic arm has 5 degrees of freedom to control and can switch to joint commands when different orientations are required at the end. Then use the joint command again to return the flange and the base to a horizontal attitude, and you can switch back to Cartesian control. A quick way to set a cartesian controllable attitude is: Just set the angle of J4 equal to-(J2 angle + J3 angle).
Motion Characteristics of the xArm6 and xArm7
Both have full 6 degrees of freedom in Cartesian space motion. For xArm7, there is one additional joint freedom, meaning more possible solutions(Null-space solution) for a specified Cartesian target, which can be attractive in robot redundancy research,collision-avoiding trajectory planning implementation, etc. For general application tasks, xArm6 can be enough, and xArm7 is recommended if more flexibility is required.
Please refer to the video about the difference in the motion characteristics of xArm5, xArm6 and xArm7.