phase - Power Electronics

IRMCF3341- Reference design
8051
running MCE
interface
software
Shared
memory
8051
memory
Motion
control
engine
(MCE)
PWM
and
ADC
AC input
Rectifier
IRAM
JTAG UART
8051 tools
MCE Tools
WASHER DRIVES
PM
motor
Fig. 7. Design tools for the washing-machine design platform include
a spreadsheet for calculating controller constants based on motor
parameters and system specifi cations. A second tool, MCEDesigner,
transmits the constants to the embedded microcontroller.
model simplifi es the fi gure, but a sampled-data model only
requires some additional scaling of the integrator-gain
parameter.
As shown in Fig. 6, the PI-controller gains are calculated
in three stages. First, to reduce the order of the loop, select the
ratio of the PI compensator gains so that its zero cancels the
pole in the motor-winding model. Next, select the integral
gain so that the closed-loop bandwidth matches the target
specifi cations. Finally, scale the integral-gain parameter by
half of the sample period to calculate the gain in the digital
implementation.
The calculation of gain parameters for the current loop is
straightforward, but the next section describes some of the
tools for tuning the velocity loop when driving the type of
complex load found in washing-machine applications.
Simplifying Drive Commissioning
The washing-machine design platform includes a digital
IC with the control algorithm already embedded (Fig. 7).
The MCE implements the algorithm in hardware based
on parameters and variables that the shared-memory area
stores. One of the available design tools is a spreadsheet that
calculates the controller constants that match the motor
parameters and system specifi cations.
The second tool is MCEDesigner, which transmits the
controller constants from a PC to an interface program
running on the embedded 8051 microcontroller. The 8051
copies the parameters to the block of shared memory before
the MCE starts running the motor.
Another important function of the 8051 interface software
is to capture trace data from the MCE, which gives the
user access to all the control-system variables. MCEDesigner
also generates speed profi les that allow users to evaluate drive
performance in the washer application. The combination
of an embedded motor control algorithm and easy-to-use
evaluation tools simplifi es the evaluation of direct-drive
motors for washer applications. PETech
For superior solutions:
Aluminum electrolytic
capacitors
Low inductance
High temperature range
Very high ripple current capability
Very long service life
More information at www.epcos.com
electronica Munich, Germany
November 14 to 17, 2006
Hall B5, Stand B5.506
www.powerelectronics.com Power Electronics Technology
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