Final Design

Final Design

The final design for the Hand for Humanoid Robot project is a compact motorized interface that allows the humanoid robot Surgie to operate da Vinci Research Kit (dVRK) surgical tools. The system combines a custom mechanical wrist-mounted tool holder, cable-driven tool actuation, Dynamixel motors, RFID tool identification, and a ROS2-based software framework. The goal of the design is to allow the humanoid robot securely attach, recognize, and control interchangeable dVRK tool tips while maintaining safe, repeatable, and precise motion.

The mechanical design attaches to the wrist of the humanoid robot and uses a user-friendly sliding track that guides the dVRK tool into the correct position. Once inserted, spring-loaded locking caps engage with the tool so the motor interface can securely control the tool’s cable-driven motion. Since dVRK tools use internal cable mechanisms to create precise wrist and gripper movement, the design connects motor rotation to the tool’s control inputs. Four Dynamixel motors are used to control the main tool motions: roll, pitch, yaw, and gripper actuation. The structure was designed to remain compact and lightweight, with a target mass below 0.5 kg, while supporting a 10 N tool tip load during operation.

The electrical system is built around an OpenRB-150 controller and four Dynamixel XC330-T181-T smart motors. These motors were selected because they provide compact size, position feedback, current feedback, and programmable motion control. The system is designed to meet the required control performance of 2° joint resolution with backlash, 60 rpm rotation speed, and 0.2 Nm continuous torque. A PN532 RFID sensor is integrated to recognize inserted dVRK tools through RFID stickers, helping the system support easy tool swapping and tool-specific control profiles.

The software system is built using ROS2 Humble, a robotics framework that allows separate software nodes to communicate with each other. This makes the system modular and easier to test. The ROS2 framework includes nodes for Dynamixel motor control, auto-zeroing, RFID detection, current monitoring, position publishing, and user input. The auto-zero function moves the motors to known home positions before operation, helping align the motor interface with the dVRK tool. The control node then converts desired roll, pitch, yaw, and gripper commands into bounded motor positions. Software joint limits, controlled sweep routines, current monitoring, and emergency shutdown behavior are included to reduce the risk of overextension or tool damage.

Functional Requirements

The final design was developed to satisfy the following functional requirements:

• Attach securely to the wrist of the humanoid robot, Surgie.

• Support a tool tip load of 10 N.

• Compact lightweight design below 0.5 kg.

• Fit, recognize, and allow easy swapping of all dVRK tools using RFID support.

• Include an auto-zero function for repeatable tool alignment.

• Operate the dVRK tool through roll, pitch, yaw, and gripper control.

• Meet control performance targets of 2° resolution with backlash, 60 rpm rotation speed, and 0.2 Nm continuous torque.

Performance Summary

The final system successfully demonstrates the main project goals: secure dVRK tool engagement, motorized tool control, ROS2 communication, and safety-aware operation. The mechanical interface allows the dVRK tool to slide into place and lock using spring-loaded caps, while the motor system controls the tool’s cable-driven motions. The design supports the required compact form factor, target tool loading, and control performance needed for humanoid robot operation.

The ROS2 software framework enables communication between motor control, RFID detection, auto-zeroing, and feedback monitoring nodes. The auto-zero process improves repeatability by returning the motors to known home positions before tool operation. RFID sensing supports tool identification and tool swapping, while current feedback provides an additional method for monitoring motor load during testing. Overall, the project shows that a humanoid robot can be adapted to operate dVRK-style surgical tools using a compact, modular, and safety-conscious motorized interface.