DESCRIPTION

The MMC-100 connects to the computer via a USB interface but appears as a serial device to spec. On modern Linux distributions the serial-to-USB driver will load automatically.

The controller is selected on the hardware configuration editor Devices screen along the lines of:

MOTORS      DEVICE  ADDR <>MODE NUM                  <>TYPE
   YES /dev/mmc100    <>  38400   8  Micos MMC-100 (Serial)

The /etc/udev/rules.d/10-spec_usb.rules file put in place by the spec Install script will ensure that the special device /dev/mmc100 is created with read/write permission for all users when an MMC-100 is connected to a Linux system via USB.

FEEDBACK MODE

The MMC-100 piezo actuators can be operated in open-loop or closed-loop modes. Controller type MMC100 on the Motor screen of the configuration editor selects open-loop mode, while controller type MMC100_E selects closed-loop mode. Alternatively, the non-standard optional parameter "feedback_mode" can be used to select the mode. Values of 0 and 1 correspond to open loop. Values of 2 and 3 correspond to closed loop. The MMC-100 manual provides details on the various feedback modes. Feedback modes 1 and 2 are reportedly quieter than modes 0 and 3. However, spec defaults are modes 0 and 3 for controller types MMC100 and MMC100_E, respectively. Note, setting feedback mode 2 or 3 has the same effect as selecting MMC100_E. Of course, closed loop mode will only work when the motor device includes an encoder.

Since positions are sent and received between spec and the MMC-100 in naturals units (millimeters), it is not necessary to configure the encoder steps parameter. In addition, the motor steps parameter is only used to set the resolution to which motor positions are rounded by spec. If using an encoder that has 5 nanometer precision, the appropriate value for the motor steps parameter would be 200000 steps/mm.

OPTIONAL PARAMETERS

spec has three types of motor parameters: standard, standard optional and non-standard optional. The standard parameters include velocity (steady-state rate) and acceleration (as acceleration time), which are configured on the main Motor screen of the configuration editor. Standard optional parameters are configured on the two additional motor parameter screens accessed by typing a lower case m from the main motor screen and include parameters such as deceleration and PID gain values. Finally, the non-standard optional parameters are parameters that are controller specific. Both the parameter name and value need to be set using the configuration editor. Each motor has its own page for configuring the non-standard optional parameters, accessed by typing lower case p from any of the motor screens.

There are a number of configurable parameters for the MMC-100. Some may be set either in the config file or by using motor_par(). If there is no configuration for a particular optional parameter, spec will leave the value unchanged in the controller.

For the MMC-100, the command

mca_par(mne, "dump")

displays parameter information as follows:

    Open/closed-loop = 3 (0,1,2,3)              "feedback_mode"
        Encoder type = 0 (0=digital, 1=analog)  "encoder_type"
    Encoder polarity = 1 (0=normal, 1=reversed) "encoder_polarity"
      Motor polarity = 0 (0=normal, 1=reversed) "motor_polarity"
 Negative soft limit = -18 mm                   "negative_soft_limit"
 Positive soft limit = 18 mm                    "positive_soft_limit"
    Jog acceleration = 250 mm/sec**2            "jog_acceleration"
Maximum acceleration = 500 mm/sec**2            "max_acceleration"
    Maximum velocity = 2.56 mm/sec              "max_velocity"
          Resolution = 8000 DAC steps/um        "resolution"
  Encoder resolution = 0.005 um                 "encoder_resolution"

            Velocity = 2 mm/sec
        Acceleration = 100 mm/sec**2 (20 msec)
        Deceleration = 100 mm/sec**2 (20 msec)
         DC deadband = 2 encoder counts
      DC settle time = 0.1 sec
DC proportional gain = 0.5 (KP)
  DC derivative gain = 0 (KI)
    DC integral gain = 0 (KD)

            Motor on = 1 (0=off, 1=on)
  Home configuration = 0 (0=neg, 1=pos)
   Home position set = 1 (0=not, 1=set)
Position theoretical = 2.00035 mm
    Position encoder = 2.00035 mm
    Encoder Velocity = 0.015 mm/sec
         Status byte = 8

The names in quotation marks in the first group are the non-standard optional parameters that can be set with motor_par() or in the config file. The second group are parameters that correspond to either standard parameters or standard optional parameters. The third group are values that are either read-only or set automatically. Refer to the MMC-100 manual for details on what the parameters mean.

Note, the values for velocity, acceleration and deceleration will not be updated to the config file values until the motor is moved for the first time.

The additional command mca_par(mne, "initialize") will download and execute a program on the associated channel to locate the limits and home position. After sending the command, one can use spec's wait() function to wait until the sequence is complete.