The CARVEC system is much more than a simple stability augmentation system. It is fully integrated into the helicopter electronics. It links directly to the receiver inputs, and drives all the servo outputs.

In order to do this, the system comes with a comprehensive ground station application which runs under microsoft windows. This allows everything to be set-up using an interactive procedure. This is used to configure every aspect of the system, including servo-movements, gain factors for the control loops and other settings such as the tail-rotor control modes.

When everything is configured, the settings can be saved to disk. They are then downloaded into the CARVEC main unit and tested.

The PC application also displays the telemetry data and/or logs it to a file on disk. Comprehensive built-in test data is also shown, along with an overall go/nogo indication.

As everything is pre-configured, the CARVEC system uses only one extra receiver channel for control. This allows HH gyro mode, RPM governor functions and stability system on/off to be fully controlled using six channels of an RC system. In a typical 8-channel system, this leaves two channels free for control of extra equipment such as positioning a camera mount.

 

System Overview

The CARVEC control system is a sophisicated flight-control computer based on the latest low-power processing and inertial sensing electronic devices. The main computing/sensing unit weighs less than 4oz (including a very tough aluminium enclosure) and consumes just 75mA of current from a standard 4.8v RC battery.

It is completely solid-state and contains no user-adjustable components. All configuration is done electronically and downloaded into the internal non-volatile memory.

Technical specifications for the unit can be seen here.

The main computing unit is usually positioned on an anti-vibration mount as close to the main-mast as possible. It is mounted above the tail-boom on this 30-size test machine to provide protection against heavy landings or uneven terrain.

The rear of the unit has four LED indicators. A Hyperbright red LED lights if any of the continuous 23 Built-In-Test results indicate a no-go situation. The others flash various codes which indicate the cause of the failure. More details of the problem are shown graphically on the PC application when the telemetry link is active.

On power-up, all non-volatile memory regions are compared against a stored checksum, and all inertial sensors are tested using special hardware which actually stimulates the sensing elements of the devices.

 

The system is flown using a standard RC transmitter. When the stability system is engaged, the right-hand stick becomes demanded pitch/roll. When the stick is moved to the right, the heli rolls to the right. When it reaches the angle demanded by the stick, it automatically stops. The amount of roll for full stick movement is configured using the PC application. When the stick is released, the heli rolls back level - following the stick movement.

With the machine on the left, only the collective pitch is being flown manually. The CARVEC computer has control over elevator, aileron, throttle (RPM governing) and tail-rotor pitch (heading-hold).

Due to the active control system, the helicopter responds to the stick movements as quickly as it normally responds to regular cyclic input. Some other types of stability augmentation actually fight the pilots inputs - giving the machine a sluggish feel.

The system also provides attitude information to a module designed to control/stabilise an on-board camera mount - see the mount-controller page.