LocoKit

Mechanics

The building blocks of the Locomorph robots, are kept simple, in order to make each block light and cheap to produce. The building kit consists of the following modules

  • Rods forming the skeleton of the robot
    • The rods have a standard dimension of 4mm, but can be of different materials in order to facilitate the ability to create different stiffness's in the structure.
  • Joints with ball bearings, able to rotate continuously.
  • Fixed joints used to build the structure
    • The rotating and the fixed joint is the basic components enabling the constructor to build the desired structure. These components are produced in aluminium because this material is more sturdy than ABS plastic from our 3D printer.
  • Components for mounting the motors
  • Mounting blocks for the wire system
    • The wire systems was introduced in the first prototypes of LocoKit as a way of transferring actuation power from the motors onto the legs of the robot, but have since then not been used in the system due to problems with ineffective. The wire systems have however not been removed from the system since we hope at a later time to be able to reintroduce it.
  • Components for integrating springs into legs
    • By creating components for implementing springs in the legs of a robot, we hope that it will make it possible to get elastic leg behavior similar to what is seen in a Spring Loaded Inverted Pendulum (SLIP) model.

Contact person: Jørgen Christian Larsen

Electronics

The development of electronics is a constant ongoing process. We have now switched to our new and most advanced platform ever based around a GumStix module - GumStix


The structure of our GumStix platform is shown in the image just above. the idea is, that the two top boards, the "Processor Board" and the "Power Board", are mounted together in the robot. One robot only contains one of each of these board. Communication to all of the peripheral motor boards happens through a 6 wired connection. There is no dedicated sensor board in the system for that simple reason that sensors can be connected on the Processor Board or any of the Motor Boards in the system.

Processor board

The main components of our new electronic platform is "Processor Board", which is an interface board for the GumStix module. Besides interfacing to the GumStix this board provides some onboard sensors as well as a number on sensor inputs.

The GumStix board have the following specifications:

  • Interfaces to a Gumstix Overo Air standard processor board, 600MHz OMAP3, 512MB RAM
  • Runs Angstrom Linux, but other distributions are possible
  • Onboard accelerometer and gyroscope
  • General sensor interface
  • 8 gpio ports
  • 4 analog inputs
  • 1 I2C interface
  • 2 Buttons and 5 LEDs

Contact person: David Brandt

Power board

To support the LocoKit with a stable power supply, we have designed a Power Board to do just that.

The Power Board have the following specifications:

  • A 6S LiPo battery provides the power
  • Fuse for short-circuit protection
  • Battery undervoltage protection is implemented in hardware
  • Voltage is regulated to a stable 24V
  • Maximum cont. current 10A
  • Efficiency of 90-95%

Contact person: David Brandt

Motor board

We have chosen to use Maxon motors in our system simply because they provide great stability, efficiency and power density. On top of this they are designed in a way that for science project makes it possible to overdrive them in order to get even more power out of them. For the same reason have we also made the board cobatible with many of the connectors from Maxons Brushless motor series.

The Motor Board have the following specifications:

  • Controls 1 BLDC motor
  • Interfaces to most Maxon BLDC motors
  • Designed for 24V, 48W
  • 48MHz ARM7 processor for time critical control and motor commutation
  • 4 GPIO multiplexed with analog inputs for local sensor interface

Contact person: David Brandt

Software

All types of hardware needs some sort of software. We are currently working on two different platforms in the project, which is also why we for the time being are using two different software setups.

Embedded Linux

On our GunStick platform we are using an embedded Linux distribution which gives us a lot of benefits because a lot of things are being handles automatically by the system, allowing us to focus on the development of the control systems for our robots.

Contact person: David Brandt

To make a connection between the lov-level software running on the robot, to high-level commands, a "locoapi" have been created as a link. This link will provide control over all functions of the system and naturally include data-logging as well. The user of the system can either program directly on the robot in C using this API, or use the webpage to control the robot

Contact person: Kasper Stoy

To make it very user-friendly to get started on using the system, we have implemented a web-server, hosting a webpage that runs of the robot it self. This webpage makes it possible to start controlling a quadruped robot using a very simple controller. Data from sensors on the robot is also passed on to the webpage and display in a live graph making allowing the user to see the impact of parameter changes live. The webpages also allows the user to generate a report of the setting on the robot to make it easier to reproduce the data obtained.

Contact person: Ulrik Page Schultz and Jørgen Christian Larsen

Overview of the software structure

 


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