Auto Position (Gait)

If your robot uses servos (humanoids, hexapods, arms, creatures, etc.), you can think of Auto Position as an easy animation system: you pose the robot, save that pose, then build a sequence of poses that plays smoothly.

In robotics, a gait is a repeating movement pattern used for locomotion (walking/crawling). Different robot designs use different gaits: a humanoid often uses a biped walk, while a hexapod uses a multi-leg crawl. Auto Position helps you build those patterns without manually coding every tiny servo move.

There are two versions of this skill:

• Auto Position (Movement Panel): Includes on-screen direction buttons (Forward/Reverse/Left/Right/Stop) and integrates with ARC’s movement system. Only one Movement Panel can exist in a project.
  Open Movement Panel version
• Auto Position (Non-movement panel): No direction pad—use it for animations, gestures, arms, heads, etc. You can add multiple instances of this version.
  Open Non-movement panel version

Not sure what a movement panel is? Read this overview: What is a Movement Panel in ARC?

Think of a flipbook: each page is a pose (Frame). Flipping pages in order is the animation (Action).

The smoothness comes from ARC automatically calculating how to transition between servo positions. This is commonly called motion planning and is related to inverse kinematics concepts. If you want the science details, see: Inverse kinematics.

1. Add the skill in ARC: Project → Add Skill → choose the Auto Position version you need.
2. Create Frames (poses): Open Configuration → Frames and set servo degrees for each pose you want.
3. Create an Action: Open Configuration → Actions, add your frames to the sequence in the order you want them played.
4. Tune the movement using Steps and Delay (and optional ramping).
5. Run it: Use the main window Execute button (or a script/ControlCommand) to play an action.

Imagine a simple robot arm with two joints (shoulder + elbow) and a gripper. “Pick up cup” is one complete Action, but it’s easier to build it as multiple Frames: start position, approach, close gripper, lift, and so on.

1) Create the Frames

Frames are snapshots of servo angles. You don’t need to program each servo movement manually—just define the important poses.

After creating frames, you’ll see a list of frames and their servo positions:

2) Add Frames to an Action

An action is a list of frames plus transition settings (how fast it moves, how smooth it is, and optional scripts).

When moving from one frame to the next, Auto Position doesn’t “teleport” servos to the new angles (unless you use Jump To). Instead, it calculates intermediate points so all servos arrive at the next pose at the same time.

Example: Steps = 5, Delay = 20
Auto Position examines the biggest angle change among all servos in that transition. If the largest change is 75 degrees and steps are 5, then 75 ÷ 5 = 15 increments are needed. ARC sends those increments with a 20ms delay between them.

Servos with smaller angle changes automatically use smaller per-increment changes so that all servos finish together.

Some smart servos/controllers (ex: Dynamixel) can do smooth acceleration in hardware. Many basic hobby servos/controllers cannot. When hardware acceleration is not available, Auto Position can simulate smooth movement using software ramping.

How to configure ramping (simple approach)

1. Set Steps to the fastest maximum step you want to use during the middle of the move (example: 10).
2. Set SW Ramping to any value above 0 (example: 1000).

What ramping does

• Starts with smaller steps (soft start)
• Uses your full Steps value around the middle (normal speed)
• Ends with smaller steps (soft stop)

Note: If SW Ramping is 0, no software ramping is used.

This video shows Auto Position used to create a walking gait for a large 3D-printed hexapod, plus how it can be controlled with other ARC skills.

A frame stores a servo position for each servo (in degrees). When Realtime Update is enabled, changing a value moves the robot immediately.

How to edit a servo position (two methods)

1. Click and drag the degree value up/down
2. Right-click the degree value and type a number

Important frame value notes

• 1–180: standard servo degree positions
• 0: releases the servo (or stops a continuous rotation servo)
• -1: skip this servo for this frame (keeps its current position)

Actions are where you turn frames into an animation or gait. You select a frame, choose how to transition into it, and add it to the sequence list.

You can export your frames/actions to a file and import them into another ARC project or another Auto Position instance. This is helpful for backups and for sharing gaits.

• 1. Export: saves an .autoposition file
• 2. Import: loads .autoposition or .ezb files

If ARC warns that a frame already exists, it is often because you attempted to import the auto-generated PAUSE frame. Unselect it during import.

Tip: You can export from one version and import into the other as long as the servo configuration matches.

Every Auto Position ControlCommand() is listed in ARC under the Cheat Sheet tab. Here are common examples:

ControlCommand("Auto Position", AutoPositionAction, "My Action 1")
ControlCommand("Auto Position", AutoPositionFrame, "My Frame 1")
ControlCommand("Auto Position", AutoPositionFrame, "My Frame 1", 50, 3)  # Delay=50, Steps=3