Press Release
Contact:
Alicia Bowers
alicia.bowers@gefanuc.com
410-242-0300
FOR IMMEDIATE RELEASE
Whedco Adds New Stall Detection to Stepping
Motor Cube™ for Intelligent, Sensorless Feedback
ANN ARBOR, Mich.
— Whedco, a subsidiary of GE Fanuc Automation, has added a new stall detection feature to the Stepping Motor CubeTM with DeviceNetTM. The new sensorless stall detection capability provides accurate, user-configured motor stall feedback to the control system and allows users to avoid costly encoders, additional cables, and more complex programming.“Most stepping motor applications are designed without position feedback. This open-loop configuration relies on the stepping motor not to stall in order to achieve its desired position,” explained Jeff Christensen, president and CEO of GE Fanuc’s Motion Business. “Theoretically, an application can be designed well within the motor's stall torque limits. But, when real world constraints are taken into consideration, the possibility of a stall condition increases. This problem can be solved most cost effectively through sensorless stall detection.”
The Stepping Motor Cube with DeviceNet features an advanced stall detection algorithm that determines whether the motor is in motion. Based on this algorithm, an intelligent decision is made in order to declare a stall condition and alert the controller. With stall detection configured, a stall condition faults the Stepping Motor Cube. The Motor Cube's following error status bit also represents a fault, where a following error is a stall condition. This bit is accessible with either the I/O (implicit) or explicit DeviceNet messaging protocols.
The Stepping Motor Cube offers three different parameters to help “tune” the stall detection algorithm for a specific application or desired result. These three parameters are stall velocity threshold, stall sensitivity, and bus voltage. The bus voltage parameter defines the DC motor power voltage used in the system (24-48 Volts DC). When the bus voltage is set to 0, the stall detection algorithm will be disabled, allowing the user to selectively apply stall detection.
The stall velocity threshold sets the velocity when the stall detection activates. For example, if this threshold is set to 10 RPS, the Stepping Motor Cube will activate the stall algorithm at velocities greater than or equal to 10 RPS.The stall sensitivity parameter represents the time in milliseconds in which the Motor Cube senses motor stall before it will actually fault the controller. Stall sensitivity has the advantage of desensitizing the algorithm to external forces such as mechanical resonance. These three parameters offer the user more flexibility to achieve the desired results for a particular application and can be accessed both implicitly and explicitly with DeviceNet.
Getting the Lowest Possible Velocity Threshold
Stall detection typically becomes less accurate at speeds less than 4 RPS. In
applications in which the profile never achieves a high velocity, it is possible
to get the Stepping Motor Cube's stall detection feature to perform well –
even at speeds as low as 1 RPS – by increasing the stall sensitivity time.
If the motor performs very short position moves at low velocities, just
ensure that the motor will achieve a speed above the stall velocity threshold
for at least twice the time set in the stall sensitivity parameter.
Achieving the Fastest Possible Detection Time
Users can achieve the Stepping Motor Cube's fastest possible stall detection time in two ways:
1) reduce the stall sensitivity time so that the controller will react more quickly to a stall; 2) use a
higher target velocity with a higher stall velocity threshold. In control systems in which the motor runs at speeds over 4 RPS, a lower
stall sensitivity time can be used because the stall algorithm provides more accurate detection results at faster speeds.
Stall detection can be used in both the position and velocity modes in the Stepping Motor Cube.
Whedco's Stepping Motor Cube is a space conscious, high-performance integrated controller/amplifier and NEMA 23 motor with DeviceNet that fits easily into systems where panel space is limited. Three motor frame sizes and several motor windings are available with a 3 Amps rms continuous rating to manage torque levels from 50 to 175 oz.-in. Input power requirements are 24-48 Vdc single-phase at 2.4 Amps. The Stepping Motor Cube with DeviceNet supports the DeviceNet Position Controller Profile's I/O and explicit messaging protocols. Either protocol may be used to monitor the fault status and set parameters within the controller. The Cube can serve with up to 63 other industrial devices on a single network. An LED provides Motor Cube device and network diagnostics to identify system faults such as undervoltage and overvoltage on single or multiaxis systems.
About Whedco and GE Fanuc Automation
Whedco, a subsidiary of GE Fanuc, designs and manufactures servo and stepping motor control products that lead the motion control industry in hardware simplicity, integral control and drive solutions, overall system performance, and flexible control architecture, including networking. DeviceNet is a digital, serial multidrop network that connects industrial controls and devices like Whedco’s DspMotion controllers and the Stepping Motor Cube. DeviceNet is a nonproprietary network governed by the Open DeviceNet Vendor Association (ODVA).
GE Fanuc Automation is a leading global supplier of industrial control systems and is a joint venture between GE and FANUC, Ltd. of Japan. GE Fanuc products and services include CIMPLICITY® manufacturing enterprise-wide software, nano to high-end PLCs, a wide range of CNCs, motion control systems, operator interfaces, industrial computers, CO2 and YAG lasers, and a wide range of integration and customer support services. Headquartered in Charlottesville, Va., GE Fanuc is part of GE Industrial Systems.
About GE Industrial Systems
GE Industrial Systems is a $6 billion global leader in manufacturing products used to distribute, protect and control electrical power and equipment, and supplying product and service solutions for commercial, industrial, residential and utility applications. GE Industrial Systems is one of GE's major businesses.
For more information on Whedco DeviceNet applications or servo and stepping motor control systems, visit http://www.whedco.com. Or contact Whedco at:
| Whedco Incorporated | Phone:(734) 665-5473 ext 127 |
| 1050 Highland Drive | Fax:(734) 665-6694 |
| Ann Arbor, MI 48108 | e-mail: Stacey.Anttila@gefanuc.com |
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Stepping Motor Cube is a trademark of Whedco Inc., A Subsidiary of GE Fanuc North America, Inc. CIMPLICITY is a registered trademark of GE Fanuc Automation North America, Inc. DeviceNet is a trademark of the Open DeviceNet Vendor Association (ODVA)