I want to control three AC servo motors with a computer or a microcontroller. I am confused about what kind of communication protocol should I be choosing for the servo drive. The input to the servo drive is a time dependent function of position or velocity.
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\$\begingroup\$ Have you chosen the servo motor already. \$\endgroup\$– User323693Jan 18, 2017 at 7:47
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\$\begingroup\$ I think you would need two computers to get this done. One receives location information and executes it, by moving the motor or by stop the load from moving it. A second to generate the instructions. The first would be small and cheap. The second one could be anything, a laptop, or another small and cheap one. Between the two computer there are a lot of options for communication, depending on your requirement like data rate, cable length, etc. Between the first computer and the motor there would be a motor drive circuit and it communicates with the motor drive usually through PWM or analog. \$\endgroup\$– user3528438Sep 1, 2017 at 3:03
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\$\begingroup\$ Keap in mind that popular desktop OSes are not real-time. Depending on your setup you may experience unacceptable delays solely due to thread switching and scheduling. \$\endgroup\$– jaskijNov 9, 2017 at 9:33
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2 Answers
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Controlling AC Servo Drives from PC or Micro-controller depends on which communication mechanism is used.
Manufacturers of Industrial AC Servo Drives implement different communication protocols to their products, deciding which one is best fitted in your application is depending on a number of requirements, such as: communication speed, number of Master/Salve devices in your system, distance between Masters and Slaves, maximum number of Slaves in your system.
Differences Between Communication Mechanisms
- Rs-232
- Single Master / Single Slave Protocol.
- Limited communication speed (Max 115 kbit/sec).
- Limited length of signal wires.
- Rs-485
- Single Master / Multi Slave Protocol (up to 127 Slaves in the same system).
- Limited communication speed (Max 115 kbit/sec).
- Extended length of signal wires.
- CAN Bus
- Multi Master / Multi Slave Protocol.
- Moderate communication speeds ( Can reach 10 Mbit/sec or more).
- Ether-Cat
- Single Master / Multi Slave Protocol (up to 127 Slave devices).
- Extremely fast communication speed (up to 100 Mbit/sec).
- Extended length of signal wires.
Last of all your application will decide to use one of these protocols depending on the requirements given above, sometimes its not required to use a powerful communication protocol due to it's not essential in your application and its going to add more unwanted cost.
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If you have not yet choosen the Servo drive, probably your best bet is to choose one with TCP/IP, Ethernet/IP or even Modbus TCP/IP. IMHO, and for my experience, these are the easiest to use from a computer, or even a microcontroller. I know ABB, Parker or Yaskawa have drives with this protocols, though I've only used ABB ones. Sure you can find plenty of other brands/models out there.