Actin  Version 5.5.5
Software for Robotics Simulation and Control
Manipulator Configuration

Using the Manipulator Configuration Dialog

The manipulator configuration plugin enables setting joint and end effector level placements and data display.

The manipulator configuration dialog is a dock widget, which means it can float separately from the main view, or dock with the sides as seen in the figures below. The dialog can be used to read the numerical values of joint positions of a manipulator, as well as set them to specific values. The same can be said of the end-effector placements. To display the dialog, click on the configuration button in the toolbar. This dialog has two tabs: Joints and End-Effectors. the dialog will appear with the "Slider" button.

Slider Button
Dock widget floating
Dock widget docked

Changing Joint Positions

In "Joints" tab shown below, the dialog displays the joint positions of a manipulator in a tabular format along with the lower and upper limit of each joint. The user can select to view the joint positions of another manipulator (if there are any) from the drop-down box in the upper left corner. Also displayed is the position of the "fixed link". For manipulators with a fixed base, the fixed link is always the base link. Note that the drop-down list for "Fixed Link" is greyed out because this particular manipulator has a fixed base.

To change the joint position state of the selected manipulator, the user can stop the simulation, ensure that "use joint control" is not checked, and then use the sliders to set the joint state of the manipulator.

'Joints' tab of the manipulator configuration dialog

To control the joints using the control system, ensure that the simulation is running, "use joint control" is checked, and the manipulator has the joint control motion constraint set active. This method of controlling individual joints uses the joint control end effector set, which constrains the position, velocity, and acceleration of each joint. The user can change the joint values in one of two ways. The first method is to set a value directly into the cell. In the figure below, the value of "Elbow" is being edited. A change that the user makes to a joint value will be validated against those limits before the change can take effect. Alternatively, the user can simply slide the slider in the rightmost column. Sliding to the left will decrease the joint value while sliding to the right does the opposite. Not only can the joint values be changed, the values of the base position and joint limits can be edited as well.

Editing joint value

If the "Update joint values" check box is checked, the slider position and joint values will update as the end effector is moved. This feature displays useful information about where the joint position is relative to its full range.

Joint values updating in real time

Moving the Base Link

To move the base link using the dialog, stop the simulation, and edit the numerical values in the "Fixed Link" table widget. For example, if it is desired to "ceiling mount" the manipulator, then make the Z position of the base link positive, and rotate the base about the X axis (roll) 180 degrees. This can be seen below.

Ceiling mount

Changing End-Effector Positions

The "End-Effectors" tab shown below behaves similarly to the "Joints" tab. It displays all the positions (placements) of all end effectors belonging to a manipulator. Again, the values of these placements can be directly edited in the cell. In the picture above, the X position of the end-effector attached to "Wrist Roll [0]" is being edited. The rightmost column shows the links to which the end-effectors are relatively defined. If an end-effector is not relative to any link, then "None" will be shown. Although the two quantities are often equal, the desired and actual locations of an end effector can sometimes be different. The user can select which of the two he wishes to examine by selecting the appropriate radio button on the left. Note, however, that if the actual positions are selected, he will NOT be able to edit the values in the table. The user can also choose to view the end-effector positions in either the system coordinate frame or in the relative link's frame if the end effector is constrained to a position relative to another link.

End Effectors tab of the manipulator configuration dialog

Using the Joint Configuration Dialog

The joint configuration dialog is used to configure the positive and negative joint ranges, joint offset, joint direction, and joint velocity constraints of the manipulator. To show this dialog, stop the simulation then click in the edit menu bar then "Joint Configuration".

Joint Configuration Dialog

Here you can change the joint ranges, joint offset, and max. joint velocities. The flip direction checkbox is used to reverse the direction rotation of a joint. To actually apply the joint rates to the control system, you must click "Apply".