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ELECTRICAL ACTUATOR IN MECHATRONIC DESIGNS?

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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. 





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