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    Mobile Robot (.sddm)

    This tutorial builds the document of a wheeled mobile base, using the Clearpath Jackal (skid steer, four wheels) of the Quick Start. The document belongs to a Strider node (sodero.mlc.NAME).

    Before You Start

    1. On the Station, add a Controller › Strider node, for example jackal, and an Actuator gateway for its wheel motors (Nodes and Connections).
    2. Select the Strider node and click Edit Stellar Designer.
    3. In Create robot definition, choose the template that matches your drive:
    Template Drive
    Differential drive 2WD Two driven wheels and casters
    MiR250 differential Differential drive of a MiR250
    Skid steer 4WD Four fixed driven wheels that slide when turning
    Mecanum 4WD Four mecanum wheels, omnidirectional
    Swerve 4WD Four steered and driven wheels
    Ackermann Car-like steering

    The template sets the drive type, which decides how body velocities become wheel commands. Then change its dimensions to those of your robot.

    Step 1: Chassis Structure

    Chassis Structure
    Chassis Structure of a skid-steer base

    Step 01 Chassis Structure ① shows the body and the wheels of the base.

    Body ②:

    Field Meaning
    Template The drive type of the template, for example skid_steer_4 (read-only)
    Length, Width, Height Outer dimensions of the body
    Base Origin Z Height of the robot's base frame above the floor (normally the wheel radius)
    Track Width Distance between the left and right wheels of a differential drive

    Wheels ③: one card per wheel, for example Wheel-fl. The template sets the wheel names and their roles:

    Template Wheels Role
    Differential drive 2WD, MiR250 differential left, right drive
    Skid steer 4WD, Mecanum 4WD fl, fr, rl, rr drive
    Swerve 4WD fl, fr, rl, rr drive_steer
    Ackermann front_left, front_right, rear_left, rear_right steer at the front, drive at the rear
    Field Meaning
    Role Read-only, set by the template: drive (driven), steer (steered) or drive_steer (driven and steered)
    Radius, Width Wheel size
    Offset X, Offset Y, Offset Z Wheel position relative to the base frame (X forward, Y left)

    Constraints ④ opens the wheel's drive limits in the right panel ⑥: max_speed and max_accel of the wheel.

    Wheel constraints
    The constraints of the front-left wheel, with its diameter and width in the 3D view

    Display ⑤ changes the 3D view; the unit menu ⑦ changes the display units.

    Skid-steer wheels slide sideways when the robot turns, so the robot turns less than the wheel speeds suggest. The skid-steer kinematics use the wheels' Offset Y: turn the robot in place by a known angle and increase the left and right Offset Y until the odometry matches the real turn. The simulated Jackal of the Quick Start, for example, uses an effective Offset Y of 0.441 m.

    Step 2: Robot System Parameters

    Robot System Parameters
    Robot System Parameters of the Jackal
    Group Fields Meaning
    ROBOT Total mass, Max payload, Center of mass, Body inertia Mass properties of the robot
    ENVIRONMENT Gravity vector Normally (0, 0, -9.81) m/s²
    MOTION Max linear speed, Max angular speed, Max linear accel, Max angular accel Limits of the body velocity. Strider and the Navigator never exceed them.

    Step 3: Actuator Mapping

    Actuator Mapping
    Four actuators driving the four wheels

    Connect each actuator of the gateway to the wheel it drives (or steers), as for a manipulator (Manipulator › Actuator Mapping). The order must match the gateway: in the Jackal's gateway, actuator 1 is the front-left wheel, 2 front-right, 3 rear-left, 4 rear-right.

    A mobile base uses the mapping only to know which actuator drives which wheel; leave the INFLUENCE FACTOR at 1. The wheel kinematics already account for the left and right side. If a real wheel still turns the wrong way, invert the motor's direction in its drive, for example by writing the drive's polarity parameter as a start-up SDO (EtherCAT Gateway).

    Step 4: Verification

    Click Verify. Stellar Designer checks the chassis structure, the system parameters, the actuator mapping and the configuration files.

    Verification
    All checks passed: skid steer, 4 wheels, 4 actuators

    Export .sddm saves a copy of the document to your computer.

    Try the Robot

    Start the gateway and the Strider node, open Strider, choose Twist, switch the servo on and drive slowly (Strider). Check that:

    • Forward drives forward and every wheel turns the right way,
    • Turn Left turns counterclockwise (seen from above),
    • the odometry on the Status page matches the distance and angle actually driven.