Sparkfun AVC: Postmortem

ATR5 did not compete in the 2010 Sparkfun Autonomous Vehicle Competition (Apr. 17) as planned.  Pictured at left are several failed Electronic Speed Controllers which were the last in a series of hardware and software issues that led to the forfeit.  Though operating well within their stated capacities, two of the ESCs caught on fire; the third merely melted.  A more reliable (a.k.a. more expensive) backup model [Traxxas Velineon VXL-3s] turned out to be unusable for PID control.  [Reversing...

ATR5-b1: Power steering tests

Sparkfun AVC

ATR5 (Hydra) will be competing in Sparkfun's 2010 Autonomous Vehicle Competition (AVC). The competition takes place in on Saturday, April 17.  ATR5 weighs about 270kg (600lb)  and must be towed to the competition in an enclosed cargo trailer. Fortunately, Sparkfun is located just nine hours' drive away, in Boulder, Colorado. The objective of the AVC is simply to autonomously travel about 1000 feet around a rectangular warehouse structure.  The primary goal is to achieve the shortest run ...

ATR5-b1: Steering mount (completed)

ATR5-b1's steering is actuated by a 1.5hp retrofitted winch. A previous post detailed the steering requirements [120lb-in torque, 540 degree total rotation] and the winch spool mount [wherein the spool is bolted to a rectangular aluminum assembly which is in turn hose-clamped to the steering wheel]. The winch base -- containing the motor and planetary gearbox -- must be affixed to the chassis framework to provide the leverage to actuate the steering wheel. Moreover, the winch must be ...

ATR5-b1: Steering winch spool mount

Steering wheels are ubiquitous, effective, and easy to take for granted. In the absence of power steering, they deliver an enormous force -- 400 pounds (1.8kN) in the case of ATR5 -- to rotate the front wheels with a user input of only 20 pounds (89N). Unlike other actuation points that interact only with the vehicle itself -- throttle, gearshift, clutch, ignition -- the steering wheel is directly affected by the unpredictable environment. A vehicle running smoothly at top speed across cemen...

ATR5-b1: Framework

ATR3-b1's framework corner angles are imperfect. Welding the corners into permanent angles is one obvious solution, but welding is a complex art and the initial equipment expenses are high: $700 - $1300 for a MIG welder and necessary supplies.  Though a weldless build is realistically limited in strength and size, bolt-based designs only require a drill press and a pile of bolts/washers/nuts. But how to build a 3-dimensional right angle with only bolts, which allow rotation about their axes?...

Power Sources 2, or, Why ATR5 is powered by two combustion engines

Small garden tractors, such as ATR5-b0, are not designed to support heavy electrical loads.  Their engines contain integrated alternators to power headlights and maintain the starter SLA, with an output around 40 watts.  This might be sufficient for logic electronics, but actuation and lighting add at least 50 to 100 average watts.  Even optimally efficient CFL or LED headlights will add 35 watts, and the physical actuators (especially steering) will add another 30 to 60W average.  [For instance...