The main challenges were met by building a non-linear analog proportional steering amplifier with potmeter feedback control and steering wheel, and integrating this with a plastic mechanical car model. The amplifier was a power darlington with hysteresis and variable feedback, and worked quite well even at high steering rates and accuracies. I also made a PWM to voltage control converter for it, and experimented with radio control units, builts from a 3 meter (illegal) FM transmitter and common radio set. I managed to get is to workm=, but the steering and drive motors RF disturbance rendered it too position sensitive to be reliable.
A bit later I built several PWM speed control units, finally
resulting in a lego motor with high efficiency, wide range speed
control, with as piece de la resistance a integrated motor
EMK based speed control feedback loop. The fun part was not
to use a tacho dynamo, but to use the 'off' time of the pwm
pulse to measure the voltage the moter itself generated as
a speed feedback control voltage. One has to filter well, mind
the collector=brush bounces, make sure the whole thing doesn't
oscilate, compensate for the rotors coil properties, but
I managed to get a quite good result. Using another lego motor
as a tacho generator worked notacibly better, especially in the
very low rpm range, but the result was very usefull.
The response rate was fast, a model car could lift its front wheels when the speed control is opened quickly, not at all to full speed, and letting a model drive very slowly over a unequal level terrain keeps it almost perfectly running at unchanged speeds running up or down hill.
To make the model more self sufficient, for instance fins its own
way back, or present innocent bystanders with a menu
controlled interaction option, a notebook could be glued on top of
it, or neatly integrated of course.
In combination with the camera, the option range explodes, path finding, auto return, mpeg coding, etc.
Everybody knows wether baloons, I guess they are about a meter
or so in diameter, and my estimate (from comparing with small
helium filled children's balloons) would be that they could
carry at least somethnig in the order of a kilogram of weight.
Standard use is to attach measurement electronics to it, let it up, possibly on a wire, and gather the data. I don't think there is any height or position control in them, and have started to think about the possibility of giving them both, as an alternative for model choppers which are quite noisy, in need of quite some fuel, dangerous to be around not at all trivial to control, and probably to vibrating to do high quality video imaging from.
The main way to control a zeppelin is to change the volume or weight to control its height, and to give it a propulsion system to change its position and compensate for the wind. There is no principal reason why a 1 meter model couldn't be fitted with the same capabilities, electrical plane propulsion systems exist commercially, which could be used in a 90 degree angle to giv a symmetrical balloon positional drive, and a electronically controlled pump could control the amount of gas in the baloon to compensate for air pressure changes and height control. This could be a piston type pump connected with a tube to the ballon opening and a fixed volume resevoir, or a serve could be fitted with an arm that presses or releases a portion of the (flexible) balloon volume.
The whole system sneed to be powered, which would be most easily possible using standard technology such as high power density rechargable cells, or a combination of a light 2 stroke engine with a generator and a resevoir battery. More advanced would be the use of energy cells, gass turbines (could probably be made quite quiet and effective).
Having the power and the 3D control facilities in a light enough version to be carries by the balloon, with some room left for electronis, the challenge is to make the balloon stable and nicely remote controllable. The directions in need of stabelizing are rotational and translational. There are gyroscopes that are used in model choppers that could provide the rotational stability which when the electronics and propulsion units are gondeled or at least highly assymetrically attached (xy motors and props on the bottom), to compensate for one (z axis) rotaional compensation, either through an added motor or using the xy propulsion system, or another set of small propulsion units could also compensate for forward rotation momentum and provide more controllable stability in the other rotational directions as well. I should mention that recently, very leightweight, accurate and small electronic variations of gyroscopes are available on the basis of piezo sensors.
Position stability should be split in xy stability and height stability. XY stability can be based on peizo or other acceleration sensors fitted with elecronical integrators and of course included in a control loop as the feedback for each directional drive engine. Alternative could be optical (image processing based, would require a camera, non foggy wether and a microcontroller, DSP, notebook or equivalent), radio controlled, e.g. gps unit based, or based on distance measurement devices.
Principally the same holds for height measurment, with the probably not very optimal addition of a air pressure based height meter (too sensitive to air pressure changes from other sources combined with accurate (cm range) height control). A interesting alternative could be to use a laser or ultrasound (what is the range of these devices?) based distance measurement to the ground. This would be fast, easy, cheap, accurate, and work under most circumstances except fog or very non-reflective surfaces, and could be combined with the acceleration or image based translation estimation in two beam version to compensate for ground height irregularities.
The thing could be radio controlled, but if some processing possibilties are available and some extra weight can be carried, a gsm, preferably even of the sattelite based type could be fitted to have all around the world control. Phone lines can carry enough data for global commands, and could even carry very low bandwidth mpeg and certainly highly compressed images. The point of adding a global positioning unit would be that the balloon can find its own way (a world map on cd rom in a notebook might fit in a larger balloon diameter version) to its destination and back, and can be used to always find it back by phoning it up for its coordinates, within 30 or 10 meter accuracy at least.
Solar power: a meter or so effectively lit baloon area can deliver a 100 watts or so in good sunlight. Gues in the tropics or the sahara you could squeeze out even more.
Integrated parabolic dish in the baloon, flexible material with silver foil coating, stabalized by baloon rotation and tilt to form a high bandwidth and quality beam connection with a ground station for high bandwith computer or video link.
Use of the above to direct sunlight captured through a transparent outer baloon unto a steam turbine driven generator in the optical centre.
current high tech research thoughts Considering a lot of work has been done on mini and even micro motor, power and exlectronic systems, one may wonder wether a 10 cm version may also be feasible, or even smaller ?