Stepper Position Maintenance Mode SPM, Error Limit

Stepper Position Maintenance Mode (SPM)

The Galil controller can be set into the Stepper Position Maintenance (SPM) mode to handle the event of stepper motor position error. The mode looks at position feedback from the main encoder and compares it to the commanded step pulses. The position information is used to determine if there is any significant difference between the commanded and the actual motor positions. If such error is detected, it is updated into a command value for operator use. In addition, the SPM mode can be used as a method to correct for friction at the end of a microstepping move. This capability provides closed- loop control at the application program level. SPM mode can be used with Galil and non-Galil step drives.

SPM mode is configured, executed, and managed with seven commands. This mode also utilizes the #POSERR automatic subroutine allowing for automatic user-defined handling of an error event.

Internal Controller Commands (user can query):

QS	Error Magnitude (pulses)

User Configurable Commands (user can query & change):

OE	Profiler Off-On Error
YA	Step Drive Resolution (pulses / full motor step)
YB	Step Motor Resolution (full motor steps / revolution)
YC	Encoder Resolution (counts / revolution)
YR	Error Correction (pulses)
YS	Stepper Position Maintenance enable, status

A pulse is defined by the resolution of the step drive being used. Therefore, one pulse could be a full step, a half step or a microstep.

When a Galil controller is configured for step motor operation, the step pulse output by the controller is internally fed back to the auxiliary encoder register. For SPM the feedback encoder on the stepper will connect to the main encoder port. Enabling the SPM mode on a controller with YS=1 executes an internal monitoring of the auxiliary and main encoder registers for that axis or axes. Position error is then tracked in step pulses between these two registers (QS command).

QS = TD − TP ⋅ YA ⋅ YB

Where TD is the auxiliary encoder register(step pulses) and TP is the main encoder register(feedback encoder). Additionally, YA defines the step drive resolution where YA = 1 for full stepping or YA = 2 for half stepping. The full range of YA is up to YA = 9999 for microstepping drives.

Error Limit

The value of QS is internally monitored to determine if it exceeds a preset limit of three full motor steps. Once the value of QS exceeds this limit, the controller then performs the following actions:

DMC-1700/1800

Chapter 6 Programming Motion • 121

DMC-1800, DMC-1700 specifications

The Galil DMC-1700 and DMC-1800 are advanced motion controllers widely recognized for their high performance and versatility in the automation and robotics industries. These controllers are designed to meet the demands of complex motion control applications, providing users with enhanced features and innovative technologies that optimize motion precision and efficiency.

One of the main features of the Galil DMC-1700 is its ability to handle up to 8 axes of motion control. This capability makes it suitable for a range of applications, from simple point-to-point movements to intricate trajectories in multi-axis systems. In contrast, the DMC-1800 extends this functionality, supporting up to 64 axes, making it ideal for large-scale automation environments.

Both models leverage Galil's powerful programming interface, which simplifies the development of motion control applications. The DMC-1700 and DMC-1800 controllers utilize a high-level programming language that supports advanced motion commands, including linear interpolation, circular interpolation, and complex motion profiles. This feature allows users to implement sophisticated motion sequences seamlessly.

In terms of connectivity, the Galil DMC series offers multiple communication options, including Ethernet, RS-232, and CAN bus, ensuring compatibility with various hardware and enabling easy integration into existing systems. The controllers also come equipped with digital and analog I/O ports, providing flexibility for sensor feedback and actuator control.

The advanced technology incorporated into both the DMC-1700 and DMC-1800 includes on-board PID control, which ensures precise motion control through closed-loop feedback. This results in improved stability and accuracy, particularly in high-speed applications. Additionally, the controllers offer extensive diagnostics and monitoring capabilities, allowing for real-time performance analysis and troubleshooting.

Another notable characteristic of these motion controllers is their compact design, which offers space-saving advantages while maintaining high processing power. Their robust construction and ability to operate in challenging environments make them suitable for a wide range of industrial applications, from CNC machining to assembly lines.

In conclusion, the Galil DMC-1700 and DMC-1800 motion controllers stand out due to their high-performance capabilities, advanced programming features, and flexibility in connectivity. With their ability to handle complex motion control tasks efficiently, these controllers are invaluable tools for engineers and manufacturers looking to enhance their automation processes. By integrating Galil's innovative motion control technology, industries can achieve greater precision, speed, and reliability in their operational workflows.

Galil DMC-1700, DMC-1800 user manual Stepper Position Maintenance Mode SPM, Error Limit

Models: DMC-1800 DMC-1700