The rotor or armature in ACTUATOR?

The rotor or armature is the movable part on the shaft, which is placed in the bearing of the stator. The rotor has also copper windings that can generate a force when the windings carry a current in a magnetic field. For a continue force the current direction in the windings must react on the value of the magnetic field. For direct current motors this phenomenon is called commutation. Consist the rotor of permanent magnetic material then the stator windings must have carry current depending of the rotor position. Induction motors working according to the induction principle. The rotor consists of short-circuited bars or windings. There is no commutation. At last the rotor can consist only of magnet iron. The generation of force is according the reluctance principle. The rotor iron follows a moving magnetic field. Because the rotor has to guide the magnetic field from one side to the other side of the stator it is nearly totally made of magnet iron. Exception of this construction are the so called air gap rotors and permanent magnets rotors. The form of the rotors can be like a cylinder, a disk or like a cup. The cup and disk forms are the air gap rotors, they have a low inertia. That is why those motors are very capable for situations with high accelerations and decelerations (servo applications). In case the armature moves from left to right it is called a linear actuator (lineator). The working principle is the same as for rotational actuators, but the choice for linear movable actuators is much greater. The reason is that there are so many different type of lineators and mostly custom made.

CLICK HERE FOR MORE DETAILS

The stator in actuator?

                      The stator has a physical and a constructional function. First it is the closing way for the magnetic fields and made of magnet iron. Magnet iron is a general name for all kinds of iron that has favorably properties for magnetic fields. Second the stator gives protection and solidity to the actuator. Next it has often some possibilities for assembling as screwing holes, assembling shields and sockets. The bearings of the shaft are also mounted on the stator. The stator has copper windings for generating a magnetic field in the air gap or generating an magnetic force. The windings can be replaced by permanent magnets with the same function as the stator windings. For decreasing the magnetical losses the stator is mostly made as a laminated core structure. In small mechatronic products the stator is highly integrated with the whole construction. 

CLICK HERE FOR MORE INFO

The general running principle of actuators?

The actuator has an electrical side and a mechanical side. The most important principle is that current in an electrical conductor move inside of a magnetical field. Such actuators has the ability to convert electrical energy to mechanical energy and vice versa. The energy conversion takes place in and around the rotor. It is easy to explain the conversion with the Lorentz-force law. The actuator is working in motor mode when electrical power is transformed to mechanical power. It is in generator mode as mechanical power is transformed to electrical power. When an actuator gets both electrical and mechanical energy input it is a dissipator (plugging mode). This mode can be used as a brake. Figure shows schematically the electrical mechanical converter with the possible energy flows. A magnetic field is necessarily for the conversion, which gives always losses of electrical, mechanical and magnetical nature. The mechanical losses are ventilation, the static and viscous friction; electrical losses are conduction (copper) losses. The magnetical losses can be iron losses (eddy current) or indirect from leakage fields. In chapter 2 the magnetical losses will be described. All the losses caused an irritating heat, which reduces the functions of the actuator.

CLICK HERE FOR DETAILS

PRINCIPLE AND CONSTRUCTION OF AN ELECTRICAL ACTUATOR?

         The actuator consists of a not movable part called the stator and a movable part the rotor or armature. Both parts are separated by an air gap, whose thickness can variate between about 0,1 mm to 2 mm. Magnetic an air gap is a disadvantageously property and should be as small as possible. Both the stator and rotor can contain windings or permanent magnets. As described above the important parts are:
The stator
The rotor
The windings

CLICK HERE FOR MORE DETAILS

ELECTRICAL ACTUATOR IN MECHATRONIC DESIGNS?

- The power. 

               There is an electrical source needed for the power for actuator and electronic controllers. Examples are the AC- main voltage supply 230/400 V 50 Hz, a battery or a generator. It will be clear that the used power influenced the choice of the actuator.

- The convertor.

             This part is responsible for current and voltage for the actuator needed for realizing the desired movements of the mechanical load.. The controller gives input signal for the convertor. Sometimes the convertor and controller are combined to one unit. The feedback of the load (position, speed) and the current of the actuator controls the convertor. Examples are frequency controllers for induction motors, controlled current sources for direct current (DC)-motors, servo-amplifiers and rectifier circuits.

- The actuator.

             The conversion of electrical energy to mechanical energy is done by the actuator and vice versa. Examples are step-motors, induction motors, relay, magnetical valve.

- The transmission. 

         Through the transmission the actuator is connected to the load. The transmission is an adjustment between the mechanical behaviour of the actuator and the load. The transmission is frequently a source of error (friction, margin, backlash), that is why the transmission is avoided and sometimes the actuator is direct coupled to the load (direct drive). Examples are a magnetic transmission, cogwheels and slip transmission.

- The load. 

           The load is the whole of desired movements of an object or a tool. The movements can be linear or rotational. Examples are rotation with a constant speed, go to a position with a defined accuracy and a movement of a mass accordently with a speed profile.

- The controller. 

         This part is the heart of the drive system. Dependent on reference input signals and the sensor signals, the controller will react so that the whole system is working alright. Sometimes the protection of the drive system is integrated with the controller. The controller exists for a great part of electronic devices (micro-controllers). In some cases the converter and controller build as one unit. The data processing is more and more done in a digital way. Also the modern sensors generate digital signals. This is one of the reasons that software plays an important role for controllers. The Digital Signal Processor is a complete computer system with parallel data processing and often used as controllers. They are very fast.

- The sensors. 

         Several quantity of the drive system has to be measured as data input for the controller. Those devices are called sensors or transducers, they transform a physical quantity into an electrical signal. In figure some incoming lines for the controller connected with a sensor. The sensor signals define the mechanical behavior of the load and the electrical behavior of the actuator. Some sensors generate signals for protection (end-switches). Examples are optical transducers for position, speed, resolvers, tachogenerators and Hall-transducers, current and voltage transducers. 

CLICK HERE FOR MORE DETAIL

GIVEN AN EXAMPLE FOR AUTOMOTIVE SYSTEM?

An Automotive Example 

A  example is the Antilock Braking System (ABS) found in many vehicles. The entire purpose of this type of system is to prevent a wheel from locking up and thus having the driver loose directional control of the vehicle due to skidding. In this case, sensors attached to each wheel determine the rotational speed of the wheels. These data, probably in a waveform or time-varied electrical voltage, is sent to the microcontroller along with the data from sensors reporting inputs such as brake pedal position, vehicle speed, and yaw. After conversion by the ADC or input capture routine into a digital value, the program in the microprocessor then determines the necessary action. This is where the aspect of human computer interface (HCI) or human machine interface (HMI) comes into play by taking account of the “feel” of the system to the user. System calibration can adjust the response to the driver while, of course, stopping the vehicle by controlling the brakes with the actuators. There are two important things to note in this example. The first is that, in the end, the vehicle is being stopped because of hydraulic forces pressing the brake pad against a drum or rotor—a purely mechanical function. The other is that the ABS, while an “intelligent product,” is not a stand-alone device. It is part of a larger system, the vehicle, with multiple microcontrollers working together through the data network of the vehicle

CLICK HERE FOR MORE RESULT

WHAT ARE THE ELECTRO MECHANICAL ELEMENTS USED?

ELECTROMECHANICALELEMENTS REFER TO

Sensors

A variety of physical variables can be measured using sensors, e.g., light using photo-resistor, level and displacement using potentiometer, direction/tilt using magnetic sensor, sound using microphone, stress and pressure using strain gauge, touch using micro-switch, temperature using thermistor, and humidity using conductivity sensor

 Actuators

DC servomotor, stepper motor, relay, solenoid, speaker, light emitting diode (LED), shape memory alloy, electromagnet, and pump apply commanded action on the physical process

FOR MORE INFORMATION CLICK HERE