Emf meter free download 320kbps,electricity outage doncaster east gp,emergency checklist piper warrior names - PDF 2016

Hi, here we provide you APK file of "App EMF Meter APK for Windows Phone" to download and install for your mobile. Systems and methods for controlling a polyphase brushless direct current (DC) motor (42) are described.
Charles Phillips et al; “Digital Control System Analysis and Design”, Third Edition, Prentice Hall Publisher, NJ 07732, 1995.
TECHNICAL FIELDThis invention relates to systems and methods for controlling a brushless DC (direct-current) motor.BACKGROUNDBrushless DC motors, also known as self-synchronous or electronically commutated motors, may be used in a variety of mechanical systems, including motor vehicles and aerospace systems.
One system includes a meter (14) coupled to a motor terminal (A, B, C) and adapted to produce a range of digital output values (44) representative of a motor terminal signal from which a back EMF signal is derivable. The system of claim 1, further comprising a buffer coupled between the motor terminal and the meter and configured to scale terminal signal values to a selected range. The system of claim 1, wherein: the monitoring circuitry is configured to update the monitoring values in the memory. The system of claim 1, wherein: the monitoring circuitry is configured to generate monitoring values that include a maximum or a minimum of the back EMF signal during one or more previous driving cycles. The system of claim 1, wherein: the monitoring circuitry and the control circuitry are implemented in a controller coupled to the meter. The system of claim 7, wherein: the controller is configured to calculate a motor commutation time based on the phase-to-phase zero-crossing identified in the back EMF signal during the subsequent driving cycle and a phase-to-phase zero-crossing identified in the back EMF signal during a previous driving cycle. The system of claim 9, wherein the meter is adapted to sample motor terminal voltages in a non-conducting motor phase at times when each conducting motor phase is being driven.
The system of claim 9 wherein the meter is synchronized with the PWM circuit so that the back EMF signal is derived from the samples of the motor terminal signal at the minima of spike voltages resulting from the PWM circuit. For example, brushless DC motors may be found in automotive engine cooling systems and in heating, ventilation and air-conditioning (HVAC) equipment. The system (10) also may include a controller (16) that is coupled to the meter (14, 42) and is operable to monitor the range of meter output values and to compute a motor commutation time based upon a monitored local minimum meter output value and a monitored local maximum meter output value.
A brushless DC motor typically includes a plurality of windings (or coils) wound about a stator, and a plurality of permanent magnets mounted on a rotor.
A pulse width modulation (PWM) circuit (26) may be provided, and the meter (14, 42) may be synchronized with the PWM circuit (26). An electronic control system switches current in the stator windings in a process known as commutation.
Zero crossings in the back EMF signals are identified based upon direct measurements of the signals at the motor terminals.
The sequential switching of current through the motor windings produces a magnetic flux that rotates the rotor. The buffer preferably is configured to scale the terminal signal values to a selected range. The buffer may include a voltage divider.The motor commutation time preferably is computed based upon an identified phase-to-phase zero crossing in a back EMF signal.


The controller may be configured to store a local minimum meter output value and a local maximum meter output value every motor terminal driving cycle.
In accordance with this inventive method, a range of signal values representative of a motor terminal signal from which a back EMF signal may be derived is monitored. Over the range of monitored signal values, a local maximum signal value and a local minimum signal value are stored.
In this way, the invention avoids the sensors and complex circuitry, such as an ASIC or a plurality of comparators, that typically are used to determine when zero crossings occur.
1A is a block diagram of control system and a driver for a polyphase brushless DC motor.FIG. 1B is a plot over time of a voltage signal at a terminal of a motor in a linear mode of operation.FIG. 1C is a plot over time of a voltage signal at a terminal of a motor in a PWM mode of operation.FIG. 2 is a block diagram of a control system, a driver and a buffer coupled between the control system and a polyphase brushless DC motor.FIG. 4A shows plots over time of signals applied to the transistors of a three-phase inverter driving circuit and the voltages at the terminals of a brushless DC motor in a linear mode of operation.FIG. 6A shows plots over time of output signals of two timers configured to implement the method of FIG. 6B is a flow diagram of a method of controlling a polyphase brushless DC motor implemented using two timers.DETAILED DESCRIPTIONReferring to FIG. 1A, a system 10 for controlling a polyphase brushless DC motor 12 includes a meter 14, a control circuit 16, a memory 18, and a driver interface 20. Driver interface 20 supplies control signals 22 to a driver 24, which includes a plurality of switching transistors for driving the terminals A, B, C of motor 12. The terminal drive currents are commutated to operate the motor in a stable, substantially jitterless way. The motor coils are commutated based upon information derived from back EMF voltages (VEMF) that are measured during a floating (non-conducting) driving phase of each terminal A-C.
In particular, zero crossings are identified when the floating terminal voltage is halfway between a local minimum back EMF voltage and a local maximum back EMF voltage. The time span between adjacent zero crossings corresponds to the driving voltage phase delay. In a PWM mode of operation, meter 14 is synchronized with a PWM driving circuit 26 and samples voltage values from the non-conducting phase terminal at times when the switching transistors driving the conducting phase terminals are active. Zero crossings in the back EMF signals are computed from direct measurements of the voltages at the motor terminals. Control circuit 16 preferably stores in memory 18 a local minimum meter output value and a local maximum meter output value, and computes motor commutation times based upon the stored meter output values.Referring to FIGS.
1B), each cycle of the terminal voltage has a characteristic “trapezoidal” profile over time.


The measured motor terminal voltages range between a local minimum value VL and a local maximum value VH.
Zero crossings in the back EMF signals are identified at times when the terminal voltage reaches a value that is equal to one half of the difference between the local maximum value and the local minimum value. 1C), the terminal voltage includes a plurality of voltage spikes that are the result of the PWM switching. 3, in one embodiment, buffer 42 includes a voltage divider 48, 50, 52 for each motor terminal A, B, C, respectively. In other embodiments, buffer 46 may include an operational amplifier or other circuit components that are configured to scale the motor terminal voltages to appropriate voltage range.
The resulting voltages at terminals A, B and C have the characteristic trapezoidal profiles VAN, VBN and VCN, respectively. From the zero crossing information, control system 10 may determine the proper times to commutate the motor winding.Referring to FIG. 5, in one embodiment, control system 10 controls a polyphase brushless DC motor as follows.
If the measured voltage corresponds to a local minimum (step 62), the local minimum (VL) is stored in memory 18 (step 64). If the measured voltage (VEMF) is equal to one-half of the difference between a previously measured local maximum and a previously measured local minimum (step 66), control system 10 determines that a zero crossing has occurred. Control system then sets T1 to the time (T2) of the previous zero crossing, and sets T2 to the current time (T), which corresponds to the most recent zero crossing (step 68). If the current time (T) follows the time (T2) of the most recent zero crossing by one half of the time span between the last two zero crossings (?(T2?T1)) (step 70), the motor is commutated (step 72).
If the back EMF voltage (VEMF) corresponds to a local maximum (step 74), the local maximum (VH) is stored in memory 18 (step 76). After an initial zero crossing is detected (step 78), the timers T1, T0 are reset and timer T1 is started (step 80). When the next zero crossing is identified (step 82), the value of timer T1 corresponds to the period (?t) between two adjacent zero crossings.
At this time, a commutation phase delay (??t) is computed (step 84), timer T1 is reset (step 86), and timer T0 is started (step 88).
When the value of timer T0 is equal to the computed phase delay (step 90), the appropriate motor winding is commutated (step 92) and the timer T0 is stopped and reset (step 94).
The process (steps 82-94) is repeated every motor commutation cycle.Other embodiments are within the scope of the claims.
For example, although the above embodiments have been described in connection with three-phase brushless DC motors, these embodiments easily may be extended to operate with any polyphase brushless DC motor.



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