In making Bedfellow, I basically converted my personal Queen bed into an autonomous self-driving electric vehicle. Don't let its furniture-ness fool you. There is a bit of umph behind this. The bed is capable of driving with a sustained 8 horsepower of force and is capable of peaking up to 25 horsepower for a limited time. The current top speed is unknown, but it is assuredly faster than any bed should go. There is also a lot of torque behind it. It has carried up to at least 12 people at once and has not shown any noticeable signs of slowing down.
The bed was designed to support up to 3,000 pounds worth of weight, and is built around a wooden torsion box frame. The central drive column is capable of supporting the entire 3,000 pounds in its own right. I did this in case the bed encountered a highly uneven surface and all four outer casters found themselves off the ground.
The outer casters have springs to absorb some of the shock and account for uneven surfaces. However, there is no real suspension to speak of, so it is not exactly a road vehicle. A pothole might be potentially devestating. This bed was largely designed for indoor domestic use.
The two drive wheels are centrally located underneath the bed. With this wheel arrangement, the bed is capable of turning on point like a tank by rotating the wheels opposite from one another. This makes it able to move around fairly competently in tight spaces. The motors are connected to the drive wheels by way of a 20:1 gear reduction. Without this, the whole thing would move very - very - fast. This gear reducer is basically a giant worm drive mechanism that reduces the bed's movement to gallery-friendly speeds.
There are two high-powered DC motors being controlled by two Alltrax motor controllers. These controllers are typically used in golfcarts and other electric vehicles. My specific model is capable of handling up to 400 amps. In the motor control circuit there is also a solenoid for engaging the power, and a reverse contactor for reversing motor direction. Each motor has its own seperate drive circuit and battery bank. Currently the drive system is operating at 24V, but I can be boosted to 48v for increased speed. However, traveling any faster than it is currently capable is likely not a good idea. There are also two chargers for each battery bank onboard.
The whole system is being controlled by an Arduino Mega which is reading 12 ultraonic sensors and interfacing the Alltrax motor controllers. The logic is rather simple. It is basically picking a random direction to move, checking to see if there is anything very close by in that direction, and then if all is clear - it moves. If there is something in the way, it picks another direction randomly and tries again. There are four safety bumpers which are connected to the Arduino using interrupts. If they are hit, the bed immediately stops moving and restarts its routine.
This may seem simple and arbitrary, but people interface with it as though it has intelligence and is purposefully considering them. Since this robot is rather large, people approach it as an equal and it creates a relationship between person and machine that none of my other smaller robots have ever really seemed to capture.
As already mentioned, the entire system was built around my personal Queen-sized bedframe and incorporated my actual mattress. The frame itself was a standard Ikea box frame. The aspects of the bed frame that were maintained are no longer particularly structural, but rather aesthetic. It is a bit like tearing down an entire building, but keeping the facade.