One of the Hound goals was the low cost and a short development time. To achieve this it was decided not to design a chassis and work on top of a RC car chassis. This reduced the development time and avoided all the prototyping extra costs.
We used not only the mechanical components but also the driving electronics like the electronic speed controller (ESC) and steering Servo. This meant that we had to work with a Ackerman style steering which has is advantages like an easier driving algorithm but also some disadvantages like the short turn ratio usual to this type of steering.
Chassis top view
Another main mechanical component is the camera arm which will be discussed in mechanics Part II. The arm was 3D designed from scratch in order to elevate the camera and be as effective as possible by maintaining the 2 servos in the base.
Since the main part of Hound was the ability to see, the camera had to had at least 2DOF of movement, so a pan/tilt system was installed in the arm so that the user could see various angles in front of the vehicle. Was used 2 standard hobby servos.
Pan Tilt Close up
The base between the electronics and the chassis was made using a 3.3mm acrylic reinforced with 2mm aluminum bars to prevent flex while moving.
In part II we will discuss the Arm, chassis cover and the pro/con of choosing a Crawler chassis.
One of our early prototypes was built as a senior university project. It is a small unmanned ground vehicle inspired on U.S. army’s MarcBot.
The requirements were that it would be a low cost remote operated sensor platform that was able to overcome rough terrain and at the same time be small enough to carry.
More than “just” a camera on wheels it had also to send sensor data back to the operator in a reliable and secure way.
The vehicle should be equipped also with a navigation system such as GPS in order to know the current position and in case of lost communication do is best to come back “home”.
The development time given was 6 months so time was crucial and we had to keep it simple and using mostly off the shelf products.
So we come up with the following specifications:
- Mechanical arm based on hobby servos
- RC 4×4 crawler chassis
- .net microframework compatible board
- WiFi communications
- Wireless camera
- Gas sensor
- Temperature sensor
- Laptop base station