27MHz remote control + telemetry
This future project is based on the 27MHz remote control system mentioned elsewhere on this website with the option for telemetry added. One antenna is used for both transmitting and receiving. The radio part is based on the AX5043 transceiver IC with which a half-duplex radio link is established. The following vessel data will be transmitted to shore at a rate of about 5Hz: ​
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Error status
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Configuration
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Speed (AVG & MAX)
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Depth and battery voltage
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Pitch (3D accelerometer)
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Status of piston tank end-limit sensors
Piston tanks that are equiped with a sliding potentiometer or a HALL sensor can be connected to the backplane PCB.
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An absolute 5V pressure sensor with a differential output and an offset input can also be connected to the backplane PCB. The offset is used for atmospheric pressure compensation.
The PCB assembly has been optimised for installation in the Patrick Henry model submarine. To facilitate electrical connections, all connectors are located on one side of the backplane PCB. The surface area of the backplane PCB is 60 x 100 mm. The height of the backplane PCB with plug-in PCBs is 70 mm. The front plug-in PCB contains voltage regulation circuitry, the mid the micro-controller and the rear the radio.
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The antenna in the model submarine is a shortened isolated wire dipole antenna for use inside the watertight compartment of a model submarine. It is optimised (dielectric constant) for mounting against/on the plastic material of the watertight compartment. The two dipole elements (330mm wires) are soldered on a small impedance matching PCB that amongst others provides galvanic isolation (MABA-11040). The antenna has been successfully tested for receiving and transmitting purposes and is also used as receive antenna in the non-telemetry RC option.
For telemetry and control purposes a 6-axis IMU is used to estimate pitch and forward velocity of the vessel. The algorithm is developed in collaboration with AI. A key feature is that the speed estimate must be as immune as possible to rotational motion (waves) and drift between stationary periods. To achieve this goal, techniques such as complementary fusion and ZUPT are used, amongst others. In addition to wave immunity and drift there are many other requirements, conditions and assumptions to consider. Currently the algorithm has reached such a level of confidence that field trials are no longer an obstacle.
