September 2, 2013
Working for DAGU means I need to try and design products that are not just cool to look at or play with but are also affordable and easy to use for the beginer. Sadly this balance is not easy to acheive. Usually more fun / cool functions means more complexity and cost.
Now I'm trying to ballance the scales again with a semi-humanoid robot chassis, the "Service Droid". Note I say chassis because the kit does not come with a controller or sensors. Just the body, motors and minimum number of servos (no pan/tilt). It is up to you to add your own sensors and controller. This kit is ideal for use with the "Mini Driver" or "Micro Magician" controllers as they both have motor drivers built in but it can be used with any controller and motor driver.
In order to reduce both cost and complexity the shoulder,elbow and wrist (up/down motion) is all controlled by a single, 13Kg.cm metal geared servo in the shoulder. This simplifies programming greatly while allowing three commonly used motions (reach down, pickup, extend arm upward) to be generated. The gripper is kept level at all times so that liquids won't be spilled.
Small "Black Duck" servos control the gripper, wrist rotation and sweeper. These servos are more expensive than ordinary miniature servos but they have thicker, stronger gears and a ball bearing on the output shaft that lets them work with heavier loads.
Omni wheels are used on the back instead of a caster ball / wheel for better stability and a 5x AA battery holder allows 5x 1.2V NiMh batteries to be used. This provides a stable 6V supply for over 90% of the discharge cycle which is perfect for powering servos and controllers that use LDO regulators. There is lots of room for controllers, sensors and batteries. The kit includes extra top plates if you want to add a pan / tilt kits using either standard or miniature servos.
The big gripper is designed to pick up drink bottles and cans with the fingers overlaping for holding smaller objects. The wrist can rotate 180° allowing the robot to pick up an upsidedown cup and then turn it right side up.
The small sweeper on the left arm is designed for scooping up small objects that are lying flat on the ground such as coins, bottle caps etc.
Update: I made several last minute changes to the design before I sent the drawings away to get the laser cut parts. I have now strengthened the wrist rotation system by adding 4x bearings.