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