Interstellar Pleasure Barge > Verbose

Remote Drive-By-Wire
8/2/2007 11:23 AM

control_system-1_4
95% Complete!
The electrically controlled vehicle operation system has been designed so that an operator on the upper deck of the vehicle can start, stop and steer the vehicle without having to engage any of the normal vehicle controls. Safety has been of paramount concern when designing the remote operation system, there are a handful of failsafe fallbacks should anything unexpected occur.
There are four basic parts to the electrically controlled vehicle operation system:

The Controller
...is a reconfigured NES Advanatage controller (which is the same controller that was used to control the "State of Liberty" in the movie, "Ghostbusters 2"). Only a few buttons are needed for control: left and right buttons for turning the steering wheel, a forward button that will release the brake pedal, a fast brake button that essentially "slams on the brake" and an accelerator button that will provide a smidgen of thrust (so as to overcome the inertia of a heavy vehicle at rest).
The controller has two fundamental safety features:
(1) The controller's at-rest state will prevent any movement of the vehicle. The driver will have to actively engage the controls to make the vehicle go (for instance, they will have to push "forward" to release the brake pedal). This feature is so that if the controller is released (or dropped) the vehicle will stop.
(2) An engine kill switch on the controller prevents power from reaching the engine. If the switch is opened (or the controller becomes disconnected by being unplugged or severed) the relay providing main power also opens and the engine stops.

The Steering Unit
The steering wheel has been directly connected to a low speed, high-torque 12vdc motor. Through a set of 12v, high current relays steering control is easy generated by two buttons (representing "turn left" and "turn right").

The Brake
The brake pedal is connected to a pneumatic piston with a four inch stroke. The piston pulls against a set of springs so that in its neutral state the piston is extended and the brake pedal is depressed.
The forward valve on the piston is connected to an air compressor via a 3-way switching solenoid valve. When the solenoid is energized pressurized air enters the piston's forward chamber and pulls against the springs, releasing the brake pedal.
When the relay de-energizes (manually or through a failure mode) the piston's chamber will be open to the atmosphere and the only force present in the system will be the aforementioned springs, stopping the vehicle.
Furthermore, a second 3-way relay connected to the first switches between normal exhaust (fast brake, this is the relay's unenergized state) and slow exhaust (through a needle valve to provide a non-jerky deceleration).
Further and furthermore I added a 4-way switching solenoid valve that, when energized, forces compressed air into the piston's rear chamber (and exhausts the front chamber) acting as a very fast emergency brake (this is equivalent to slamming on your brakes). The IPB stops very immediately knocking over everyone who isn't ready for it but, more importantly, enables me to avoid hitting that damn hippie who just rode his unlit bike right in front of us.
It's worth repeating here that in the event of a power loss all relays are configured so that the piston vents directly to atmosphere providing fast, safe braking.

The Accelerator
This component is yet to be built. Currently thinking involves a tubular push-type solenoid (with a short stroke) connected to the accelerator that will provide a small amount of power when a button on the controller is pressed. For safety, the solenoid's unpowered state will cause the accelerator to release
to prevent uncontrolled acceleration. This will help jog the vehicle if it gets stuck in a rut, on very loose soil or needs to ascend a short inclination.


Image Gallery: Steering Component
The various stages of the steering unit.
First version of the steering motor: a length of steel attached to the motor (which, incidentally, was built as a power-window motor). The mount for the steering unit. The circuitry for controlling the direction of the motor via a pair of L/R buttons.
See all 4 images.

Image Gallery: Brakes
The braking system.
Husky brand 1.5g, 2 SCFM air compressor. Preliminary tests show I need only a handful of psi's (~10psi) to put ~20 pounds of force on the pneumatic piston. This should work splendidly. Prototype brake piston assembly. Not shown: the spring assembly that will force the piston into the chamber when it is "at rest". The piston has a couple of springs on it now so that the ram is extended when the solenoid valve is open. I just need to install this in the IPB and add/remove springs until I get the force right.

Image Gallery: Complete
Everything all put together
95% complete control system. The steering control is at the top; the brake piston is at the bottom. The NES Advantage is the wired controller. The piston is connected, via high pressure hoses, to a set of three solenoid valves to the left. A bank of relays (black and white boxes) at the top of the electronics panel control the solenoid valves and the steering motor. The only thing missing from this is the component that will jog the accelerator should we get stuck. The NES Advantage controller I re-wired to be the pleasure barge's pilot controls. The first version of the control system attached in place. It works good! The control system, all by itself. The piston at the bottom controls the brake (there is a mess of solenoid valves and relays to its right). The steering motor is at the top, the row of black boxes screwed into a piece of wood above it are the 12v relays that control it. The black cord on the ground supplies several amps of 12vdc; the smaller brown cable provides 120vac to the second 3-way solenoid valve (which will be replaced with a better 12vdc solenoid in the final version). Hanging on the l...


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