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Jogging

Jogging moves one joint, or the tool along one axis, for as long as you hold a button or repeat a command. It is how you check a new robot, teach a pose and get out of trouble.

Joint jog

Each joint has a pair of arrows in the commander's Joint jog menu: the left arrow is the positive direction, the right arrow negative, as in Joint limits and directions. The speed slider sets the speed as a percentage of the commander's jog maximum, which is lower than the speed a program may use (Speeds). A jog stops at the joint limit.

rbt.jog_j(0, speed=0.3, duration=0.5)               # joint index 0 = J1, 30 % speed, 0.5 s
rbt.jog_j(joints=[1, 2], speeds=[0.2, -0.2], duration=1.0)
A jog command runs for duration and the arm brakes to rest when no newer jog arrives; a GUI repeats it while the button is held. Joints are indexed from 0 in the API.

Cartesian jog

The tool moves along X, Y or Z, or rotates about them, in the world frame (WRF, fixed to the base) or the tool frame (TRF, fixed to the tool). The commander's Cartesian jog menu has the six pairs of arrows and the WRF/TRF switch; a jog in the tool frame moves the tool along its own axes, which is the natural way to approach a part.

rbt.jog_l("WRF", "X", speed=0.2, duration=0.5)
rbt.jog_l("TRF", axes=["Z", "RZ"], speeds_list=[0.2, 0.1], duration=0.5)

A Cartesian jog needs a homed robot, and it can run into a singularity, where the planner cannot find joint speeds for the tool's motion: the commander stops the jog, and the Python API refuses it. Jog a joint away from the singular pose and continue (Configurations and singularities).

Jogging a robot that is not homed

Joint jog works before homing: it is how you check the directions on a new build. The positions shown are meaningless until the robot is homed, and a Cartesian jog is refused.

Both programs still check each jog against the joint limits, with a position count that starts at 0 when the board is switched on. That count puts joint 2 past its positive limit and joints 3 and 6 at or below their negative limits, so until the robot is homed:

  • joint 2 jogs only in its negative direction (the right arrow);
  • joints 3 and 6 jog only in their positive direction (the left arrow);
  • joints 1, 4 and 5 jog both ways.

A refused jog does not move: the commander logs Error: Robot jog -> Position out of range, the Python API stops the joint before it starts.

Warning

Before homing, the limits are checked against a count that does not match the arm, so they do not protect the joint: nothing stops it at its real limit except the printed blocker. Jog briefly and slowly.

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