SQUIRT

Construction:

Overview:

Most parts are from Spark Fun: the servos from Trossen Robotics and the chassis from Machine Labs.

Custom parts were made on a small drill press and band saw. The green parts are acrylic, the silver parts aluminum.

The Chassis

Even though I’ve made dozens of chassis for combat robots, I decided to go with a commercial one so multiple Squirts could easily be constructed. The MMP-8 Mobile Platform made by my friend Zak at Machine Labs was perfect for Squirt. http://www.themachinelab.com/MMP-8.html The chassis comes with 6 gear motors, wheels and a speed controller. It’s light, very tough and thoroughly tested: it’s used worldwide by police and military units.

The Servos:

To control the pan/tilt of the water gun the servos need to be fast, powerful and accurate. The Robot’s RX-64 servos are that and more. Control is over a 1Mbps RS485 Multi Drop Bus. They have a monster 888 oz. inch of torque (not 40 or 50 like a regular servo). It takes one second to spin their 300 degree arc of rotation. You have to see them in action to believe it. In addition they have embedded processors which gives back servo status. http://www.trossenrobotics.com/dynamixel-rx-64-robot-actuator.aspx

The onboard display:

The display is an Active Matrix OLED with a 2.83″ screen. It was selected because it can be read in sunlight. It takes high level graphic commands thus offloading processing duties from the other CPUs.

Current sensor, motor controller and servo status are displayed. During construction the display helped in the debugging process. Even with this help there were times when the robot drove across my keyboard and squirted me and the monitor.

Sensors:

Distance sensors are used for object avoidance and AI situational awareness. Sonar is used on the left and right (range about 5 feet) and IR on the front and rear (range about 3 feet).

The pan and tilt servos can detect if they are being moved by an outside force, like a hand pushing down on them.