Control System B-3MN1902B.1.2 Velocity (Speed) controlSetting the control mode to Velocity Control configures the FlexDriveII or Flex+DriveII as aspeed amplifier, as shown in Figure 44. Here, a speed reference is obtained from a specifiedsource.H Mint / host command (profiled)H High speed analog input (not profiled)H Analog input (profiled)H Fieldbus (profiled).The source provides a signal that can either be fed directly into the Speed controller (onlywhen using the high speed analog input source), or through a profiler. The high speedreference source is ideal for connecting to a motion controller (e.g. NextMove PCI) that willhave already profiled the signal and will provide optimum loop closure.The profiler generates a speed demand signal that smoothly changes between successivespeed targets (reference values). This is achieved by specifying acceleration anddeceleration times (see the WorkBench v5 Parameters tool). The speed demand signal is fedinto the speed controller and used, together with the speed measured from the feedbackdevice, to generate a torque demand signal. If the speed controller is tuned correctly, themeasured speed will accurately track the speed demand.Finally, the torque demand signal is fed into a torque controller, which determines theappropriate amount of current to apply to the windings of the motor. This demand current iscompared with the actual winding current measured from sensors, and a suitable pulse widthmodulation (PWM) signal is generated. This PWM signal is fed to the power electronics in thedrive.Speedcontroller Torquecontroller Power stage+ motorTorquedemand PWMSpeeddemandSpeedprofilerSpeedreferenceMeasured currentMeasured speedHigh speedspeed referenceFigure 44 - Control structure in Velocity control mode
