Integration Guide

This document provides complete integration guidance for the Alius Robot Joint Module, covering mechanical design, electrical design, software development, and system commissioning, helping you efficiently and reliably integrate the joint module into your robot system.

Mechanical Integration

Mounting Interface Design

The joint module uses a standardized flange interface, with mounting holes provided on both the input side (stator side) and the output side (rotor side). The following points should be noted when designing the robot joint structure:

1. Mounting Flatness: The flatness of the mounting contact surfaces on both the input and output sides should be better than 0.05 mm to avoid additional bending moments and abnormal bearing wear.
2. Bolt Selection: High-strength socket head cap screws of grade 12.9 are recommended, with thread locking adhesive (such as Loctite 243) applied.
3. Alignment Accuracy: The coaxiality between the output shaft and the load shaft should be better than 0.1 mm. The use of Oldham couplings or diaphragm couplings is recommended for connection.

Load Analysis

During the design phase, a detailed analysis of the robot joint load characteristics should be performed to ensure that the selected joint module meets the following requirements:

• Peak Torque: Required peak torque of the joint ≤ module peak torque × safety factor (recommended 0.8)
• Continuous Torque: Sustained operating torque of the joint ≤ module continuous torque
• Radial/Axial Load: Radial and axial forces acting on the output flange ≤ module rated load capacity
• Moment of Inertia Matching: Load moment of inertia ≤ module rotor moment of inertia × 10 (after squaring the gear ratio)

Thermal Management Design

The joint module generates heat during prolonged high-load operation. Inside a sealed robot body, appropriate heat dissipation measures need to be considered:

• Design cooling fins or heat conduction channels on the module mounting base
• For locations with densely arranged multiple joints, forced air cooling or liquid cooling solutions may be considered
• Avoid installing modules in enclosed, unventilated spaces

Electrical Integration

Power System Design

When designing the power supply system for multiple joint modules in a robot system, the following factors should be considered:

1. Power Supply Capacity: Total power supply capacity should be ≥ sum of all modules’ peak currents × 1.2 (safety margin)
2. Power Cable Routing: Star routing or zoned power distribution is recommended to avoid voltage drop in one module affecting other modules
3. Filtering and Protection: It is recommended to add EMI filters and reverse polarity protection circuits at the power input

CAN Bus Design

The quality of CAN bus wiring directly affects communication reliability. Recommended design guidelines:

1. Bus Topology: Use daisy-chain topology; avoid star connections.
2. Terminating Resistors: Install one 120Ω terminating resistor at each end of the bus.
3. Cable Selection: Use twisted-pair shielded cable with 120Ω impedance, such as Belden 3106A.
4. Grounding: Single-point grounding of the shield; avoid ground loop interference.
5. Bus Length: At 1 Mbps baud rate, the total bus length should preferably not exceed 40 meters.

Connector Pin Definition

Module-side connector (M8 5-pin Type A female) pin definition:

Software Integration

Initialization Procedure

After the robot system is powered on, the software should initialize the joint modules according to the following procedure:

1. Bus Scan: Send a broadcast “Device Search” command to obtain the node IDs and ready status of all modules on the bus.
2. Parameter Configuration: Configure the control mode, communication period, and protection parameters for each module according to system requirements.
3. Zero-point Calibration: If the system does not store the zero offset value, a zero-point calibration procedure needs to be performed once.
4. Enable Preparation: Send the “Enter Enabled State” command and check the return status from each module to confirm normal operation.
5. Enter Operation: Begin sending periodic control commands.

Motion Control Implementation

Depending on the robot’s control architecture, different control modes can be selected:

• Position Control: Suitable for trajectory tracking scenarios. The controller calculates the target position of each joint and sends it to the modules in a periodic manner.
• Velocity Control: Suitable for force control or impedance control scenarios, where the target velocity is calculated through an outer-loop force control.
• Torque Control: Suitable for direct force control scenarios, such as landing impact buffering for legged robots.

Status Monitoring and Fault Handling

The software should continuously monitor the status feedback frames from each module and promptly handle the following situations:

• Communication Timeout: If a module has not returned a status frame for 500 ms continuously, a communication fault handling procedure should be triggered.
• Overtemperature Warning: When the module temperature approaches the protection threshold, the output torque should be actively reduced or the motion planning adjusted.
• Encoder Anomaly: If the encoder reading shows jumps, the joint motion should be stopped and the cause investigated.

Commissioning Recommendations

1. Single Joint Commissioning: Before integrating into a complete system, perform individual commissioning on each joint module to verify basic functions.
2. Start with Low Gains: When performing closed-loop control for the first time, use lower control gains and gradually adjust to the optimal values.
3. Current Limiting: During the commissioning phase, set the current limit to a low value to avoid damage to the module or injury to personnel in unexpected situations.
4. Log Recording: Enable complete communication logging during the development phase to facilitate problem troubleshooting.

Frequently Asked Questions

Q: When multiple modules are powered on simultaneously, how can power surge be avoided?

A: It is recommended to use a staggered power-on strategy, enabling each module in sequence, or use a power module with a soft-start function.

Q: Occasional frame loss occurs in CAN bus communication. How can I troubleshoot?

A: Check whether the bus terminating resistors are correctly installed, whether the cable shield is properly grounded, and whether the baud rate settings are consistent.

Q: There is slight play in the module output shaft. Is this normal?

A: Slight movement of the output shaft in the unpowered state is normal (the encoder is not powered, and the reducer has a small amount of backlash). The play should disappear after power is applied and the module is enabled.