arm motors - Uvic-Robotics-Club/uvic-rover-2027 GitHub Wiki
The robotic arm uses six actuators, one for each degree of freedom (DOF). The design uses two kinds of actuators:
- Avatar Robotics M-Series: Integrated Joint Actuators using a CANopen communication interface.
- CubeMars AK-Series: Integrated robotic actuators using a manufacturer-specific CAN communication protocol.
Two of the original actuators got replaced due to internal failure. The CubeMars AK45-36 actuators were bought as replacements.
Although both motors provide joint movement and position feedback, their communication protocols and commands formats differ. The software therefore maintains separate communication interfaces for the two kinds of actuators.
For general explanations of electric motor types, gearboxes, encoders, torque, and motor control, see Motor Fundamentals
An integrated joint actuator combines the components required to produce and control rotational movement in one assembly.
Typical components include:
- Electric motor: Converts electrical energy into rotational motion.
- Gearbox: Reduced output speed and increases available output torque.
- Motor Driver: Controls the electrical power supplied to the motor.
- Encoder: Measures rotational position for feedback and control.
- Communication Interface: Allows an external controller to send commands and receive feedback.
The exact components and sensor configuration depend on the actuator model.
Unlike a bare electric motor, an integrated actuator handles much of the low-level motor control internally. The external controller can therefore command the actuator through its supported interface rather than directly controlling the motor's electrical phases.
The original arm uses Avatar Robotics M-Series joint actuators, including M4210 and M5730 models.
These actuators integrate a motor, gearbox, encoder, and driver. The CANopen version supports standardized CANopen communication mechanisms, including SDO and PDO messaging.
The exact electrical and mechanical specifications depend on the model. The following two links are the only documentation that exist for the motors:
- https://www.scribd.com/document/871659220/Catalogue-of-AVATAR-M-Series-Robot-Joint-Actuator2024?v=0.652
- https://www.atarrobot.com/harmonic-robot/m-series/M-robot-joint.html
The CubeMars AK45-36 is an integrated brushless DC actuator with a planetary gearbox and an integrated driver board.
Key specifications for the AK45-36 V3.0 KV80 include:
| Specification | Value |
|---|---|
| Motor Type | Brushless DC (BLDC) |
| Gearbox | Planetary |
| Gear Ratio | 36:1 |
| Rated Voltage | 24 V |
| Rated Torque | 8 Nm |
| Peak Torque | 24 Nm |
| Rated Speed | 40 rpm |
| Communication | CAN |
| Control Modes | Servo and MIT |
The actuator supports two control modes:
- Servo Mode: Used for conventional position-oriented control.
- MIT Mode: Supports commands combining desired position, velocity, and torque-related control.
The exact command format, feedback fields, and mode configuration can be found in the manufacturer's documentation: