Speed encoding

The phasor /, and /, are separated and then controlled separately as discussed later. For more precise speed control a pulse encoder feedback device can also be employed. The characteristics now improve to Figure 6.10. The torque can now be maintained constant at any speed, even at zero speed. 

With different approaches to monitor and control the basic parameters of the motor, i.c. 4, /, and sin 6, many tnorc alternatives arc possible to achieve the required speed variation in an a.c. machine. Control of these parameters by the use of an encoder can provide an accuracy in speed control as good as a d.c. machine and even better. 

Pulse encoder-To feed back actual speed ol the motor and the angular position of the rotor with respect to the stator at a particular instant. 

Notice that in this example, the speed of the packet is inversely proportional to the packet s spatial size. While there is certainly nothing unique about this particular representation, it is interesting to speculate, along with Minsky, whether it may be true that, just as the simultaneous information about position and momentum is fundamentally constrained by Heisenberg s uncertainty relation in the physical universe, so too, in a discrete CA universe, there might be a fundamental constraint between the volume of a given packet and the amount of information that can be encoded within it. 

The variable ERRORmj n represents the error in the position of the mandrel over an increment in TIME, in seconds. ERRORman is calculated by subtracting the actual pulses accumulated, PULSEman, from the desired number of pulses that would be generated under perfect control. The desired number of pulses for perfect control is determined by the set point speed, RPSman, revolutions per second and the mechanical gear reduction. The constant 15630 is the product of encoder counts per revolution and the thirty to one gear reduction of the mandrel. 

Fig. 4.5.11 Measured TOF and phase encoding velocity profiles from the lower, vertical center line and corresponding fits using Eq. (4.5.8). Outer cylinder rotation speed is ...

The REDOR experiment has formed the basis for a large number of ideal pulse type recoupling experiments, and later finite pulse variants, for heteronuclear dipolar recoupling. These include experiments such as frequency selective REDOR (FS-REDOR) [80], TEDOR (Transferred Echo DOuble Resonance) [25], and 3D variants of TEDOR [81, 82], which have found important applications, e.g., for measurement of intemuclear 13C-15N distances in biological solids. We should also mention that rotor-encoded variants of TEDOR, such as REPT, HDOR [83], and REREDOR [84], have been proposed for 1H13C dipolar recoupling under high-speed MAS conditions. 

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