The actuator
The actuator is the original RC transmitter sold with the toy helicopter. Some simple modifications were made to enable it as a proper interface between the human pilot, the helicopter and the computer. The objective is to be able to read the commands given by the pilot in the computer, send computer commands to the transmitter and resend them through the transmitter to the helicopter, as shown in the following figure.
Two different transmitter models were tweaked: the Silverlit PicooZ transmitter and the Walkera WK-2401 transmitter.
The first one is a two channel infrared digital transmitter. At the present moment several toy helicopters use the same electronics and the study we carried out is valid for all of them. This paper in spanish describes how the transmitter works and the circuit design that was made. At present, experiments with PicooZ are discontinued because two channel helicopters are very difficult to fly properly.
The second transmitter is a four channel PPM 2.4GHz device. There are several helicopters compatible with this transmitter, in fact any helicopter with receivers Walkera RX2410 or RX2401 are compatible. This transmitter is easier to tweak, no additional electronics are needed, and offers a four channel flight which is enough to maneuver a helicopter confidently.
Walkera WK-2401 RC transmitter arrangements
The commands of the pilot are collected through mechanical joysticks that move two analogical potentiometers each. The middle connector of each potentiometer carries a tension proportional to the joystick position. This connector, which is originally soldered to the transmitter board, is isolated from the board and its signal is taken out to two different places: one is the Advantech PCI-1711 card and the other is a switch. The switch selects its output from an outside connection or the potentiometer signal. The switch is connected to the transmitter board, where the potentiometer was previously connected.
This way it is possible to manually select the signal that the board reads from the internal source of the transmitter or an external source, which currently is computer generated and converted to analogical by the Advantech PCI 1720U card and the NI USB 6008 card. Moreover, the action commands given by the pilot can be read from outside the RC transmitter and can also be fed back to it.
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