Optimize Master-Follower

The Master-Follower feature opens SERVOsoft up to a whole new realm of Optimization - a Complete Power Group. Ie. SERVOsoft optimizes an entire multi-axis machine/robot.

In general, when optimizing the Master, the most common scenario uses the optimization target 'XBase: Time' on a Constant Velocity Master. Effectively, this means the Optimizer works to reduce the Power Group's Cycle Time by increasing the Master Constant Velocity, while meeting all constraints. However, if the Master has a Variable Velocity Sequence, this takes optimization to a much higher level.

The 'Optimizer PRO' is an option that is only available with the SERVOsoft PRO version, which includes the CAM Profiles feature, essential to take full advantage of the Optimizer.

Master: Constant Velocity Sequence

The most common optimization scenario for a Master Follower Constant Velocity application is the following:

	Optimize = 'XBase: Time' The Optimizer will work to reduce the Master's Sequence Cycle Time, which is the Power Group's Cycle Time
	Algorithm Population Size Population Size = 0 tells the Optimizer to start with the existing profile and not to seed/explore other profiles. Setting the Population Size to 0 requires that the existing sequence passes all constraints. Ie. The Optimizer must start with a solution that passes all constraints. If the existing sequence does not pass all constraints, then no solution will be found, as the optimizer will not explore any other parameter sets when Population Size = 0. If no solution is found, set a Population Size of 5 or 10 and try again.
	Algorithm Step Settings Velocity Step Setting this value provides the Optimizer with a level of detail for this parameter Default values is typically suitable; adjust as needed for accuracy, where more accuracy requires more processing time When Optimizing for Time, the Duration step value is not used For a Const Velocity segment, Accel and Jerk step values are also not used as Accel and Jerk are always 0
	At least one Additional Constraint is required as the Optimizer needs to push up against a constraint as it works to reduce 'XBase: Time'. The simplest constraint to add is: Power Group Util <= 90% All parameters for all axes must have Util <= 90% Example uses 90%, but can set to any value > 0 Evaluates the utilization for all components for all axes in the power group including infeed and bleeder modules, drives, motors, gearboxes, mechanisms, etc.
	The Segment Input Constraints provide the Optimizer the allowed range of values: Duration Set a valid Min/Max range or remove (light blue colour indicates an optional constraint) When Min/Max values are not specified, this means there is no Duration constraint, such that other constraint(s) are the limiting factor(s) when optimizing for Time. Velocity Set a valid Min/Max range In this example, set to 36 - 120 °/s, where 36 °/s is the existing segment value Unlike the Duration constraint, the Velocity Min/Max values are required to give the Optimizer a range of values to play with. Accel & Jerk Not used for a constant velocity segment where Accel and Jerk are always 0
	Suggested Parameters If not sure where to begin, the Suggested Parameters are a great way to get started Sets the Algorithm, Segment and Additional Constraints with suggested values Based on the Optimize Type, the suggested parameters tend to be "wider" and not too precise/tight to allow the Optimizer to find a good solution. The trade off being it may take longer to find an optimal solution.

Click Start and in a few seconds the solution is found...

Master: Variable Velocity Sequence

A slightly more sophisticated approach to optimize a multi-axis machine/robot, where the Master is setting the pace, is letting the Master’s velocity vary in a range. With that approach even faster cycle times can be achieved. In order to do so, the Master’s single Constant Velocity segment needs to be split into 2 or more segments. Start by right clicking on the segment and click 'Selection' -> 'Split Segment'.

Fewer segments allow the Optimizer to find a solution faster, but with the tradeoff of perhaps not quite as optimal a solution.

Now with 2 segments, click on the 'Optimizer PRO' button and adjust following settings.

	Optimize = 'XBase: Time' The Optimizer will work to reduce the Master's Sequence Cycle Time, which is the Power Group's Cycle Time
	Algorithm Population Size Population Size = 40 tells the Optimizer to seed/explore 40 random parameter sets
	Algorithm Step Settings Velocity, Accel & Jerk Step Setting these values provides the Optimizer with a level of detail for each parameter Default values is typically suitable; adjust as needed for accuracy, where more accuracy requires more processing time When Optimizing for Time, the Duration step value is not used
	Profile Type = Poly 1-5 (segments) The Optimizer will try to find a faster cycle time using Poly 5th order splines Keep in mind most common motion controllers can handle segments defined up to Poly 5th degree
	Additional Constraints Double click the 'Additional Constraints' cell to add/edit additional constraints. At least one Additional Constraint is required as the Optimizer needs to push up against a constraint as it works to reduce 'XBase: Time'. The simplest constraint to add is: Power Group Util <= 90% All parameters for all axes must have Util <= 90% Example uses 90%, but can set to any value > 0 Evaluates the utilization for all components for all axes in the power group including infeed and bleeder modules, drives, motors, gearboxes, mechanisms, etc. Motor Max Speed Margin >= 10% All motors for all axes must have Speed Margin >= 10% Additional constraints for Follower Axis components such as the "Motor Max Torque Margin" and "Motor Max Speed Margin" apply to all motors in the power group. Same goes for Transformation, Inverter, Infeed and Bleeder constraints. Spline Constraints To keep the Spline smooth, some Spline Constraints are needed. Start Vel = End Vel Ensures the spline’s velocity at the beginning is the same as at the end. This is necessary because the Master is running continuously. For this we even might set a range where this velocity might be in, here in between 54 °/s and 90 °/s. Start Accel = End Accel Ensures that the spline’s acceleration at the beginning is the same as at the end. I.e. the Master’s acceleration is continuous and within a range, here between -800 °/s² and 800 °/s². Segment Distance Overshoot Allows the distance for each segment to vary with a range, i.e. the spline’s segments can undershoot or overshoot their existing traveling distances. A limitation between -10% and 10% is good start for the first run, providing some flexibility, but not so much that the calculation run. Total Distance Ensures the Master distance will be 360 °
	The Segment Input Constraints provide the Optimizer the allowed range of values: Duration Set a valid Min/Max range or remove (light blue colour indicates an optional constraint) In this example, set to 2 - 3 s, meaning that with 2 segments, the fastest possible cycle time is 2 + 2 = 4 s, and the longest possible is 3 + 3 = 6 s, assuming all other constraints are met. When Min/Max values are not specified, there is no Duration constraint, such that the segment Duration is not a constraint when optimizing for Time. Velocity Set a valid Min/Max range In this example, set to 36 - 120 °/s, where 36 °/s is the existing segment value Accel Not specified so the optimizer can use any accel values that meet all other constraints Jerk In this case, set very large so that Jerk is effectively not a limiting factor
	Suggested Parameters If not sure where to begin, the Suggested Parameters are a great way to get started Sets the Algorithm, Segment and Additional Constraints with suggested values Based on the Optimize Type, the suggested parameters tend to be "wider" and not too precise/tight to allow the Optimizer to find a good solution. The trade off being it may take longer to find an optimal solution.

After pressing the 'Start' button the Optimizer appears with a result like this after about a minute:

So the cycle time was reduced from 5 sec to 4.2 sec only by varying the Master's velocity, while maintaining all Follower axes positions in relation to the Master's position.

Optimize Master-Follower

Master: Constant Velocity Sequence

Master: Variable Velocity Sequence

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