Within the Volts/Hz Controller compound block, insert the following blocks:
•From Blocks > Arithmetic, add a summingJunction, gain, unitConversion, and / block.
•From Blocks > Signal Producer, add a const block.
•From Blocks > Nonlinear, add a limit block.
Wire the blocks together, as shown below.
The input speed for this block is assumed to be the speed of the chuck; therefore, the gain block is needed to scale this speed up by a gear ratio of 10 since this controller affects the speed on the motor side. RPM is then converted to hertz by using a unitConversion block set to RPMÞrad/sec and then dividing the output by 2p. The value 2p is produced by using a const block set to 2*pi.
The measured speed comes from the Rotary Encoder and is in radians per second. This measurement is converted to hertz simply by dividing by 2*pi. The desired speed in hertz is fed into a summingJunction block, as well as the command input of the PID Controller (Digital) block. The desired speed directly feeds the inverter/amplifier as the feed forward component of the control. PID Controller (Digital) block output is used to correct for minor errors in the feed forward component. The sum of these two components is fed to the inverter/amplifier, the sum is limited to 70 hertz to prevent running the motor into its unstable region of control. The output of the limit block feeds the Three Phase Square Wave Inverter block. The Three Phase Square Wave Inverter block rail voltages must be set to 0 and 1, as shown below, to effectively provide logic control rather than bus level voltages:
The output of the control summingJunction block is scaled inversely proportional to frequency by using a gain block with the factor 230/60. The output is then limited between 0 and 230 volts, and defined to be a variable block with the user-defined name amplifier gain.