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Auto Position (Gait)

+ How To Add This Control To Your Project (Click to Expand)
  1. Load the most recent release of ARC.
  2. Press the Project tab from the top menu bar in ARC.
  3. Press Add Control from the button ribbon bar in ARC.
  4. Choose the Servo category tab.
  5. Press the Auto Position (Gait) icon to add the control to your project.
A gait is the pattern of movement of the limbs of animals, including robots, during locomotion. This robot skill allows robots to have customizable servo animations for locomotion and interacting with the world. Most robots use a variety of gaits based on speed, terrain, the need to maneuver, and energetic efficiency. Different robot configurations may use different gaits due to differences in their build. For example, a humanoid robot uses a bipedal walking gait while a hexapod uses a six-legged crawling gait.

Two Versions

There are two versions of the Auto Position robot skill (Movement Panel and Non-movement panel). The only difference between the two is the inclusion of the movement panel functionality. Read about what a movement panel is and how it works with ARC to learn more.


Auto Position Overview

The Auto Position skill is used to transform a group of servos into custom positions (Frames) to create gaits. The frames can be combined into actions for your robot gait. The software will automatically calculate how to transition the servo positions between frames of the gait. Like many other ARC skills, this is done with magic! That magic is "Inverse Kinematics", or otherwise known as "Motion Planning". Each frame of the auto position consists of "goal point positions" for each servo. When frames are combined into an action, there are algorithms within ARC that calculate the speed at which each servo moves to obtain the goal point position of the next frame. This skill can be used for hexapods, bipeds, or any other creation you can dream up!

How It Works

Think of a flipbook, drawing a figure on each page, and then flipping through to create an animation. The Auto Position skill is very similar. Start by creating frames for each position of the robot. Let's say we're making it dance for example. Now create a new action and add each frame of the dance to that action. When the action is played, the joints (servos) of the robot will move into each frame sequentially in the order you added them. Interested in the science behind motion planning? If so, click here.

frames-and-actions.jpg




Tutorial Creating Hexapod Gait

Here is an example of using the Auto Position to program an walking gait for a 3D printed large hexapod robot. This demonstrates the power of movement panels by also using additional skills (camera, speech recognition, joystick) to control the movements.





Main Window



1. Movement Panel
These buttons will allow you to control the directional movement of the entire robot (left, right, forward, reverse, and stop).

2. Action List
This is the list of actions that have been created. Select one and click the execute button to run one of the actions.

3. Execute Button
This button executes the selected action in the action list.

4. Jump To... and Transition To... Buttons
The "Jump To..." button instantly moves the servos into the position of the frame selected in the frame list. The "Transition To..." button moves the servos gradually into the position of the frame selected in the frame list.

5. Frame List
This is the list of frames that have been created. Select one and click the "Jump To..." or "Transition To..." Buttons.

6. Step and Speed Values
Adjust these values by click and holding the left mouse button on them or right-clicking them and entering a value in from the keyboard. These values are used for the "Transition To..." button. The lower the speed value the faster the servos will transition into the position. The lower the step value the more steps a servo will take when transitioning to the next position. The higher the step value the more multiples of degrees the servo will skip to get to the desired position.

7. Panic Button
This button will stop and releases all the servos.

8. Status Display
Displays the status of the commands that are being executed inside the Auto Position skill.

Configuration - Frames



Each frame displays values for all the servo positions (in degrees). You can modify the servo positions and the robot will respond in real-time. There are two ways to edit servo positions:

1) Left-click and hold on the degree number value to drag the value up and down.

2) Right-click on the degree number value and use the keyboard to type in the value.

*Notes:

  • In a frame, the position of a servo is between 1 and 180 degrees.

  • If the position value of 0 (zero) is selected, this releases the servo from its holding position. If the gearing allows the output gear can be moved by hand. Selecting the value of 0 for a Continuous Rotation Servo will cause the servo to stop rotating.

  • If the servo position value of -1 is selected the Auto Position skill skips the servo for that frame. The position of that servo is maintained and nothing is changed until the next frame.

  • While designing custom frames for your robot, pay attention to the stress/weight applied to servos. A servo can be pre-maturely damaged and if too much force is applied to it during the frame creation process. We suggest supporting the robot's weight while moving the servo positions of a frame. Once it looks right, place the robot down to see how it is holding.

1. Servo Positions
These are the servo positions set up inside a frame. Each number corresponds to a servo position value set up on a specific port. Enable Port Edit mode to see the port number.

2. Background Image
A background image can be added to represent your robot. Image files (.PNG and .JPG) are supported and will be stetched to fit the background area. Background area is approximately 840 x 512 pixels.

3. Port Edit Mode Checkbox
When enabled this checkbox allows the port number to be displayed above each servo position value. It also allows the port to be changed by left-clicking on it.

4. Realtime Update Checkbox
When enabled this checkbox allows the servo positions to affect the robot in realtime. This is very helpful when creating a gait for your robot.

5. New Frame Button
If you'd like to duplicate a frame, select the frame you'd like to duplicate and press the New Frame button. This allows you to easily continue working on a robot action from the last frame position the robot was in.

6. Frame List
This is the List of created frames containing servo positions. When editing servo positions for a frame, you can right-click on a frame to select the servo positions and copy them to the clipboard. This is useful if you want to create a script for moving the servos later, or if you wish to make a script for setting servo Max and Min limits. Simply right-click on a frame and select Copy Positions to Clipboard. Then paste the clipboard into a script and add the commands to move the servos into position.



7. Transition To... Button
This button moves the servos gradually into the position of the frame selected in the frame list.

8. Delay and Step Values
Adjust these values by click and holding the left mouse button on them or right-clicking them and entering a value in from the keyboard. These values are used for the "Transition To..." button. The higher the step value the more multiples of degrees the servo will skip to get to the desired position. The higher the delay value the slower it will take to get there.

9. Servo Management Buttons
These buttons will allow you to add, delete, fine-tune, and release all servos. To delete a servo first enable the Port Edit mode checkbox, then click on the Servo border, and press the DEL key on the keyboard. To fine-tune the servo positions press the fine-tune button and use the options available (Add, Subtract, Multiply, Divide, Set to, & Invert) to change the position values.



10. Clear/Change Image Button
This button allows you to delete/set your own background image for this skill. A background image will help you set up servo positions to match the physical layout of your robot.

Configuration - Actions



1. Action List
This of a list of created actions, use the action management buttons to make changes to this list.

2. Action Management Buttons
These buttons manage the action list. Add a new action, rename an action, or remove an action with these buttons. You will have to select the action in the list first to rename or remove that action.

3. Frame List
Select the frame you would like to add to the sequence list, once selected you will need to press the Add button.

4. Delay, Steps, and Speed Values
These adjustable values will set the Delay, Steps, and Speed of the frame you will be adding to the sequence list.

5. Add Button
This button takes the selected frame from the frame list adds the setup Delay, Steps, and Speed values to it, and puts it at the bottom of the sequence list.

6. This Action Repeats Checkbox
When enabled this checkbox will make the sequence list loop infintely when the action is executed. The action will continally loop until another action is executed.

7. Edit Script Button
This button allows you to add a script to the action. If the button is green no script is present. If it's blue there is a script that will be run when the action is executed.

8. Sequence List
This list contains the sequence frames (frames + values) that will be run sequentially (top-down) when an action is executed. The list can be modified using the sequence management buttons.

9. Sequence Management Buttons
These buttons manage the sequence list. You can test the action sequence with the execute button. Edit any sequence frame with the edit button. Delete a sequence frame with the remove button. Change the action sequence by moving a sequence frame up or down with the move buttons.

Configuration - Settings



1. Auto Position Start Script
This script will be run before a frame or action is executed.

2. Auto Position End Script
This script will be run after all the frames or actions in the queue have been executed.

3. Auto Position Variables
These variables contain the name of the current action and frame as well as the status of the auto position skill. If the auto position skill is excuting a frame or action the $AutoPositionStatus will be true (1), otherwise if the skill isn't running it will be false (0).

4. Title Field
This field contains the title of the auto position skill. You can change it if you'd like. *Note: Changing the title here will also change the title in the controlCommand() associated with this skill.

Configuration - Import/Export Utilities



Within the Configuration menu is the ability to Import or Export Actions and/or Frames. You can only import frames if the servo configuration matches the existing project, for obvious reasons. If the servo configuration does not match, the import utility cannot simply "guess" what servos to assign the new frames. This limits importing and exporting to projects with the same servo configuration.

If importing a frame and it already exists, a message will be displayed. Simply deselect the frame from being imported. The most common mistake is attempting to import the PAUSE frame, which is auto-generated and cannot be removed.

1. Export Button
This button exports an .autoposition file for adding to another ARC project.

2. Import Button
This button allows you to import both .autoposition and .ezb files into an ARC project.

Auto Position With Movement Panel vs Without

There are two types of auto position skills in ARC. One which has a movement panel, and one without.

1) The Auto Position With Movement Panel skill contains a movement panel, which will execute the robot gait actions for direction movement. Like all movement panels, there can only be one instance of this skill. There are predefined actions for movement directions (forward, reverse, left, right, and stop) which you can assign frames to. You can add gait frames to each action to have your robot move in a customized fashion when any control calls the robot to move a direction.

To control an Auto Position with Movement from a script, there are specific commands for it that require ControlCommand(). View the cheat sheet for available ControlCommands, or use the script movement commands (Forward(), Left(), Right(), Stop(), Reverse()).

2) The Auto Position Without Movement Panel skill can have multiple instances and does not control directional movements like a movement panel. This skill also accepts script controlcommand()s.

How to Use Auto Position Skill

1) Add the Auto Position Skill to your ARC project (Project -> Add Skill -> Movement Panels -> Auto Position Movement Panel).

2) In the Configuration menu create multiple new frames for your servo motor(s).

3) In the Configuration menu create a new action and add the frames you've created. Add some pause frames between your frames if needed.

4) In the main window select an action and press the action button.

Code Samples

Every Auto Position ControlCommand() is published in the Cheat Sheet tab. Pressing the Cheat Sheet tab will display the ControlCommands() for all skills, including the Auto Position. To execute an Auto Position from a script, you would use commands such as:

ControlCommand("Auto Position", AutoPositionAction, "My Action 1")
ControlCommand("Auto Position", AutoPositionFrame, "My Frame 1")
ControlCommand("Auto Position", AutoPositionFrame, "My Frame 1", 50, 3)

Videos




Requirements

One or more servo motors.

Resources

There are utilities for importing and exporting auto position files in the Configuration menu. The Import/Export tab will contain buttons to launch the specific utilities.