MC1141A Ver la hoja de datos (PDF) - PMD

Número de pieza

componentes Descripción

Fabricante

MC1141A

Advanced Microstepping Motion Control Chipset

PMD 

multipled by 65,536 and the result is sent to the chipset (-

127,795 dec. or fffe0ccd hex).

In this profile mode the host specifies two parameters, the commanded

acceleration, and the maximum velocity. The trajectory is executed by

continuously accelerating the axis at the commanded rate until the max.

velocity is reached, or until a new acceleration command is given.

In this way the output of the microstep generator will precisely track the

input encoder position factored by a programmable gear ratio. This can

be useful in many applications where continuous synchronization with

an external mechanism is important.

The following figure shows the arrangement for encoders and motor

drives in a typical electronic gearing application with the MC1241A

The maximum velocity value must always be positive. Motion

direction is controlled using the acceleration value. Positive

acceleration values result in positive motion, and negative values

result in negative motion.

Master

Encoder

MC1241A

Amplifier

There are no restrictions on changing the profile parameters on

the fly. Note that the motion is not bounded by position however.

It is the responsibility of the host to generate acceleration and

max. velocity command values which result in safe motion, within

acceptable position limits.

The following figure shows a typical velocity profile using this mode.

Example Velocity Contouring Mode

Vel.

change

acceleration

change

max velocity

Time

Only one of four axes shown

Motor

The total number of geared axes supported per chipset is equal to the

number of motor axes. For each motor axes the encoder input for the

same axis is used as the master position command. In addition these

master/slave combinations are fixed, with the encoder for axis 1 driving

the axis 1 microstep generator, and the encoder for axis 2 driving the

axis 2 microstep generator.

There are no restrictions on changing the gear ratio when the axis

is in motion, although care should be taken to select ratios such

that safe motion is maintained.

change max

velocity and

acceleration

There are no restrictions on switching the profile mode to velocity

contouring while the axis is in motion.

The Starting Velocity can not be changed while the axis is in

motion.

Electronic Gear

The following table summarizes the host specified profile parameters

for the electronic gear profile mode:

There are also no restrictions on changing to this profile mode

while the axes is in motion.

Trajectory Control

Normally each of the above trajectory modes will execute the specified

trajectory, within the specified parameter limits, until the profile

conditions are satisfied. For example for the point-to-point profile modes

this means that the profile will move the axis until the final destination

position has been reached, at which point the axis will have a velocity

of zero.

Profile

Representation & Range

Units

Parameter

Gear Ratio

signed 32 bits* (1/216 scaling)

-

-1,073,741,824 to +1,073,741,823

* for example to specify a gear ratio of +1.5 to 1 the value

1.5*65,536 is sent to the chipset (98,304). Alternatively to set

the gear ratio as -11.39 to 1 the value -11.39*65,536 is sent (-

746,455 dec. or fff49c29 hex.).

In this profile mode, the host specifies one parameter, the gear ratio.

The target position is generated by applying the specified gear ratio to

the encoder position of the same axis, multiplying by the specified gear

ratio and outputting the corresponding number of microsteps.

Halting The Trajectory

In some cases however it is necessary to halt the trajectory manually,

for safety reasons, or simply to achieve a particular desired profile. This

can be accomplished using one of two methods; abrupt stop, or smooth

stop.

Abrupt stops are accomplished using the STOP command. This

command instantaneously stops the trajectory generator by setting the

velocity of the axis to zero. This control mode is typically used during an

emergency stop, when no deceleration phase is desired.

Smooth stops are accomplished using the SMOOTH_STOP command.

This command causes the trajectory to decelerate at a rate equal to the

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