Texas Instruments Evaluation Module for the DRV8829 DRV8829EVM DRV8829EVM Scheda Tecnica
Codici prodotto
DRV8829EVM
#Clk Cycles =
4E6 Hz
#PPS
UART Mode
This screen is an area that offers access to a series of simple stepper control algorithms. The user can
control motor enablement, rotation rate, direction of rotation, current decay mode during microstepping,
microstepping resolution (from full step to 512 degrees of microstepping), and the number of steps the
motor should move.
control motor enablement, rotation rate, direction of rotation, current decay mode during microstepping,
microstepping resolution (from full step to 512 degrees of microstepping), and the number of steps the
motor should move.
Motor motion can only occur by using an acceleration profile. A detailed explanation of each stepper
control section is presented in the following subsections.
control section is presented in the following subsections.
4.4.1
Motor Control Frame
This frame allows the configuration and operation of the stepper with the direction as specified under the
Direction frame, with the current decay mode as specified under the Decay Mode frame and the
microstepping resolution as specified under the Microstepping Resolution frame.
Direction frame, with the current decay mode as specified under the Decay Mode frame and the
microstepping resolution as specified under the Microstepping Resolution frame.
The Motor Control frame gathers user information about the stepping rate, or motor speed. An
acceleration profile is employed to start at a programmable speed and increase the stepping rate until the
programmable desired speed is reached.
acceleration profile is employed to start at a programmable speed and increase the stepping rate until the
programmable desired speed is reached.
An internal 4-MHz timer is used to measure time and generate the steps in a timely manner. The
application software transforms the entered number of pulses per second (PPS) into clock cycles by
following the formula in
application software transforms the entered number of pulses per second (PPS) into clock cycles by
following the formula in
(2)
The acceleration profile is coded into the microcontroller to accept both Start Speed PPS and Desired
Speed PPS as clock cycle numbers. When the Start Steps command is issued (by pressing the Start
Steps button), an interrupt service routine (ISR) generates steps at the rate specified by the Start Speed
PPS parameter.
Speed PPS as clock cycle numbers. When the Start Steps command is issued (by pressing the Start
Steps button), an interrupt service routine (ISR) generates steps at the rate specified by the Start Speed
PPS parameter.
An internal task running at 1 kHz modifies the stepping rate by subtracting the Acceleration Rate
parameter until the actual stepping rate equals or is larger than the Desired Speed PPS parameter.
parameter until the actual stepping rate equals or is larger than the Desired Speed PPS parameter.
The internal task in charge of coordinating stepping rate coordination can be slowed down so that the
further increase in stepping rate is achieved at a slower rate than its inherent 1-ms period. This is done by
increasing the Time Base parameter. The Time Base parameter is zero based, so if a 1-ms period is
desired (the fastest acceleration time rate possible), a zero must be programmed in place.
further increase in stepping rate is achieved at a slower rate than its inherent 1-ms period. This is done by
increasing the Time Base parameter. The Time Base parameter is zero based, so if a 1-ms period is
desired (the fastest acceleration time rate possible), a zero must be programmed in place.
Once the Desired Speed PPS is reached, the acceleration profile ends and the motor stays running until
the Stop Stepper command is issued (Stop Stepper Button). When the stepper is commanded to stop, the
controller does exactly as it did while accelerating, but in reverse as to achieve deceleration until the Start
Speed PPS is reached, in which case the motor fully stops.
the Stop Stepper command is issued (Stop Stepper Button). When the stepper is commanded to stop, the
controller does exactly as it did while accelerating, but in reverse as to achieve deceleration until the Start
Speed PPS is reached, in which case the motor fully stops.
Whether the motor is disabled or allowed to maintain a holding torque (windings are energized), will
depend on the Disable Stepper checkbox. Its default is asserted, in which case the motor will become
de-energized after motor is commanded to stop.
depend on the Disable Stepper checkbox. Its default is asserted, in which case the motor will become
de-energized after motor is commanded to stop.
shows the acceleration profile and the role each parameter plays during speed computation.
10
DRV882x Evaluation Modules
SLMU002
–
June 2011
Copyright
©
2011, Texas Instruments Incorporated