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CANopen Programmer's Manual - Maccon.de

CANopen Programmer's Manual - Maccon.de

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<strong>CANopen</strong> Programmer’s <strong>Manual</strong> 4: Control Loop Configuration<br />

Position Loop Inputs<br />

Inputs from the trajectory generator to the position loop are <strong>de</strong>scribed below.<br />

Input Object Name/ID Description Page #<br />

Instantaneous Comman<strong>de</strong>d Velocity to which the position loop's velocity feed forward gain is 137<br />

Velocity / 0x2250<br />

applied.<br />

Instantaneous Comman<strong>de</strong>d<br />

Acceleration / 0x2251<br />

Position Command Value /<br />

0x6062<br />

Acceleration to which the position loop's acceleration feed forward gain<br />

is applied.<br />

Motor position (in units of counts) to which the amplifier is currently<br />

trying to move the axis.<br />

Position Loop Feedback<br />

The feedback to the loop is the actual motor position, obtained from a position sensor attached to<br />

the motor (most often a quadrature enco<strong>de</strong>r). This is provi<strong>de</strong>d by Position Actual Value object<br />

(in<strong>de</strong>x 0x6063, p. 137).<br />

Position Loop Gains<br />

The following gains are used by the position loop to calculate the output value:<br />

Gain Description<br />

Pp - Position loop proportional The loop calculates its Position Error (in<strong>de</strong>x 0x60F4, p. 139) as the difference<br />

between the Position Actual Value and the Position Command Value. This error in<br />

turn is multiplied by the proportional gain value. The primary effect of this gain is to<br />

reduce the following error.<br />

Vff - Velocity feed forward The value of the Instantaneous Comman<strong>de</strong>d Velocity object is multiplied by this<br />

value. The primary effect of this gain is to <strong>de</strong>crease following error during constant<br />

velocity.<br />

Aff - Acceleration feed forward The value of the Instantaneous Comman<strong>de</strong>d Acceleration object is multiplied by<br />

this value. The primary effect of this gain is to <strong>de</strong>crease following error during<br />

acceleration and <strong>de</strong>celeration.<br />

These gains are accessed through the sub-in<strong>de</strong>x objects of the Position Loop Gains object (in<strong>de</strong>x<br />

0x2382, sub-in<strong>de</strong>x 1-6, p. 139).<br />

Position Loop Output<br />

The output of the position loop is a velocity value that is fed to the velocity loop as a command<br />

input. This output is associated with two objects, as <strong>de</strong>scribed below.<br />

Output Object Name/ID Description Page #<br />

Velocity Command Value / Velocity that the velocity loop is currently trying to attain. In normal 144<br />

0x606B<br />

operation, this value is provi<strong>de</strong>d by the position loop and is i<strong>de</strong>ntical to<br />

the Position loop control effort.<br />

Position Loop Control Effort /<br />

In<strong>de</strong>x 0x60FA<br />

Optionally, the velocity loop can be controlled by one of several<br />

alternate control sources. In this case, the Velocity command value<br />

comes from the analog reference input, the digital PWM inputs, or the<br />

internal function generator.<br />

Normally, this value is provi<strong>de</strong>d by the position loop. When the velocity<br />

loop is driven by an alternate control source, the Position loop control<br />

effort object does not hold a meaningful value.<br />

Modulo Count (Position Wrap)<br />

The position variable cannot increase in<strong>de</strong>finitely. After reaching a certain value the variable rolls<br />

back. This type of counting is called modulo count. See bit 21 of the Manufacturer Status Register<br />

object (in<strong>de</strong>x 0x1002, p. 60).<br />

Copley Controls 131<br />

137<br />

137<br />

139

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