Actuators

Electro-mechanical actuators are at the forefront of Muirhead’s vision for the future. Investment in a new design centre, engineers with proven track records and recruits from partnerships with universities has seen the team grow into one of best in Europe. Some of our actuators can have built-in electronics or be controlled from external sources. The following designs are just a sample of what is attainable. Our design team would welcome the opportunity to discuss your requirements and help define the optimum solution.

Electro-mechanical actuators transform electrical energy into mechanical energy in the form of linear or rotational movement. The source of this movement comes from an electric motor and its controller. In case of a rotary actuator the following components are also typically present: gearbox, clutch/brake and angular position sensor. In the case of a linear actuator (see cut away view below) the following components are typically present: gearbox, Acme or roller or ball screw, clutch/brake and linear position sensor. All the components are integrated in a housed assembly. In all cases an electronic control unit controls the various functions to obtain the required command trajectory.

Detailed below is a demonstration actuator currently available at our shows for viewing

Medium Size Electro-Mechanical Actuator

Major Components

The major components of the linear actuator shall comprise:

• Ball Screw
• Gearbox (optional)
• Brushless Motor – Dual Channel, redundant windings
• Electronics
• Commutation Sensor
• Linear Position Sensor

Levels of redundancy

For an Actuator Sensor, we have the following levels of redundancy

Four Fin Actuator

Illustrated right is our Four-Fin Actuator. It has been modeled on a tail fin and is controlled by an electronic interface that regulates the movement of its fins, for more information please see our videos in the media centre.

VCU's

This is a fuel/air control system for a missile. The VCU (valve control unit) regulates the air/solid propellant mix during flight. The system consists of a brushless DC motor roller screw drive and an electronic control interface that provides data transfer with the missile system and control motor commutation. Key design features enable this control unit to provide short term high performance and operate at very high temperatures, whilst retaining a long shelf life.

Applications

In-Flight Refuelling Probe

The pictured actuator system was successfully designed and manufactured by Muirhead Aerospace in response to a specific customer requirement. The requirement was for an actuator to provide accurate rotary motion in order to extend and retract an Air Refuelling Tank System probe. Aircraft could then be retro-fitted, enabling in-flight refuelling. This actuator was designed to meet stringent military specification requirements for in-flight refuelling. The main design factors are as follows.

• High Power
• High Accuracy Position Sensing
• Fuel Resistant
• Brake Assembly / 34 Nm Holding Torque
• Gearbox / coupled to a leadscrew (ratio 55:1)
• Brushless Trapezoidally Driven DC Motor (15,500 rpm)
• Resolver / Accurate Absolute Probe Position Feedback
• Actuator Output Torque / 30 Nm

Fuel Valve Actuation

Hybrid stepping motor design is a key element of Muirhead's capability. The stepping motor is designed as a double wound unit to provide two actuation functions, relating to fuel metering and stator vane positioning. Features include provision of a fuel pressure case and linear motion via a ballscrew.