Electronics


First Prototype

Sensors and Communication System Overview

The initial design idea of the GIMBiped, envisioned a 3D biped fully actuated by linear motors. The platform is intended to be self sufficient with all the controllers, computers, sensors, actuators and power source included in the robot. The first version of the GIMBiped draw near to this concept, as can be seen in the figure. This first prototype version does not include the power supply in the platform, and it is powered trough a cable.

The biped robot is originally named 'The Sway', the name which was changed later to GIMBiped to better relate its development with the CoE GIM. The preliminary prototype has 4 actuated degrees of freedom per leg, and an extra degree of freedom in the center of the hip, which coupled the rotational movement of both legs around the waist. The ankle's lateral DoF is not actuated. The upper body carried the Power Distribution Box (PDB), the Walking Algorithm Computer (WAC) and the linear Motor Controllers (MC). The Linear Motors (LM) in charge of moving the leg sideways in the frontal plane, were also located in the upper body, as were the motors which control the joint in the center of the hip.

Later the original platform was temporarily modified to match the 2D compass configuration of a model tested in a simulator and to have preliminary experiments. Further details on the mechanical design can be found in the following publications in Publications.

Regarding the sensor and communication infrastructure the figure below illustrates the original concept. The goal is to develop a completely distributed and modular system, which could be easily upgraded or modified.


Original idea for the Information Distribution Infrastructure

In the original infrastructure the main processing units were two PC104 embedded computers. One, named Motor Hub, was in charge of sending positioning commands to the linear motor's controller using CAN protocol, and the other PC104, named Sensor Hub, was responsible to collect all the sensor's data. A third computer named WAC was in charged of generating the walking patter for the biped, and a fourth computer named Central Computer (CC) was in charge of managing the communication between them. The linear motors, used to drive all the biped's joint, have built in sensors which are capable of measuring the motor's position, velocity, temperature, input voltage and current. The data can be acquired through their CAN interface. The linear motors' controller have their own PID positioning control. These controllers receive control commands and send motors variables data through CAN interface that can be accessed from the Motor Hub. The Linear Motors and their controllers are commercially available products from the LinMot company. Drivers developed in Linux to control the motors (generic and with GIMnet) can be found in the Downloads section.

All the computers, Sensor Hub, Motor Hub, WAC and CC, were also alternatively connected to a network for remote access using the GIMnet communication infrastructure. The GIMnet is a specially design network architecture, which was initially used to control the GIMBiped. GIMnet was built over TCP/IP protocol and is a combination of Client-Server and Peer-to-Peer network. GIMNet allows the robot to be controlled remotely in real-time, and the user can communicate through firewalls since it has built-in VPN capability. The GIMnet is used in all the robotic platforms of the CoE GIM and initially it was planned to be used in the GIMBiped as well. However problems with variable and long delays over the network connections limited the real-time capabilities, and the communication infrastructure was modified later. For further information please refer to the GIMnet page.