Starter kit expedites your development with feature rich multi-protocol servo drive.
The Festo CMMT-ST (019-3554) is an eminently compact servo drive for use with stepper motors, brushless DC (BLDC) motors and EC motors rated up to 300W (at 48 VDC). It is well suited to positioning tasks with both point-to-point and interpolating movement solutions. This, single multi-protocol drive supports PROFINET, EtherCAT, Ethernet/IP and Modbus TCP.
The CMMT-ST drive also features integrated safety functions STO (SafeTorqueOff) - Cat 3, Ple / SIL 3 / SILCL 3 to ensure safe operation. While energy recovery and energy management features ensure sustainable operation and increased efficiency.
The CMMT-ST Starter Kit packages the drive together with a Festo EMMT-ST stepper motor, cabling and connectors, to enable rapid evaluation and solution development. In this article, we take a look at the starter kit, before moving on to explore the CMMT-ST drive in a little more detail.
Kit Contents
Upon opening the starter kit box we are presented with the servo drive, stepper motor and a graphic which shows their interconnection and highlights key features. Web links and handy QR codes are also provided for the associated documentation and software.
Removing the drive we see that this is of a robust construction and with a variety of connections, which we will come on to in due course.
On the side of the drive, we find data such as the part number and first Ethernet MAC address, along with key specifications such as the maximum input, motor output and its IP20 rating.
A 42mm flange-size stepper motor is included in the kit.
The part number and summary data are provided on a label on the side of the motor, which is from the Festo EMMT-ST range. This particular part, EMMT-ST-42-S-RM, decodes to:
- 42mm flange size (42)
- Short length (S)
- Angled connector, adjustable (R)
- Absolute encoder, multi-turn (M)
EMMT-ST motors are also available in 57 and 87mm flange sizes, with medium and long length bodies in addition to short, and single-turn encoders as well as multi-turn. Featuring a variety of rated outputs, peak torque and rotational speeds etc. Models are also available with holding brakes. For further details, see the Festo EMMT-ST datasheet.
A cable is included in the kit, which is pre-terminated on one end for the stepper motor, with the other end terminated by ferrules.
Finally, an assortment of connectors for use with the drive are also included.
CMMT-ST Servo Drive
Taking a closer look at the servo drive we see that there is a robust steel tab extending out by the X6 and X1C sockets, which are for motor and reference/limit switch connections respectively. The tab provides a combination of cable shield connection and strain relief.
Just above X6 there are sockets labelled X2 and X1A, which are for encoder and I/O connections.
The final front panel connection is an RJ45 port labelled X18, which is a standard Ethernet port and used for parametrisation, commissioning and diagnostics.
On the top of the drive there are two more RJ45 ports, labelled XF1 IN and XF2 OUT, which are provided for real-time Ethernet (RTE) — i.e. fieldbus — use.
On the underside, there is a single connection marked X9 for load (24-48 VDC) and logic (24 VDC) voltage supplies, and where required a braking resistor may also be connected via X9.
With a 24 VDC load supply the drive is capable of supporting motors rated up to 150W, while at 48 VDC load supply this increases to 300W. The logic supply should be 24 VDC ± 15 %.
Installation
The CMMT-ST can be fitted to a DIN rail or affixed directly to a wall or enclosure chassis plate.
An example system structure can be seen above, with the servo drive connected to a suitable power supply and motor, the RTE ports connected to an Ethernet-based fieldbus, and the standard Ethernet port cabled to a laptop for parametrisation.
More about installation and wiring can be found here: Servo drive - Installation - safety sub-function.
Interfacing
Three switches on the top of the drive are used to set the fieldbus protocol. These can be set to either directly configure the CMMT-ST to one of PROFINET, EtherCAT or Ethernet/IP+Modbus TCP, or for the fieldbus protocol to be set via software parametrisation.
The XF1 IN and XF2 OUT ports are IEEE 802.3-2012 Ethernet with a maximum transmission rate of 100 Mbps. These RTE ports can only be utilised for fieldbus communications, with all parametrisation, commissioning and diagnostics communications via standard Ethernet port X18. In keeping these two classes of communications completely isolated, it means that different network architectures can be employed, with security and quality-of-service (QoS) etc. as appropriate.
The drive has 4x Ethernet MAC addresses, the first of which is printed on the label, with the other 3x being consecutive numbers based on the first. MAC addresses 1, 2 and 3 are allocated to the device profile, with address 4 allocated to the communication interface X18. The device can be configured via DHCP or alternatively set to have a static IP address.
Festo Automation Suite
CMMT drive diagnostics.
Parametrisation, commissioning and diagnostics are carried out using the PC-based Festo Automation Suite and CMMT-ST plug-in. This provides a familiar, easy-to-use component-based display for use with not only motor drives, but also controllers and other Festo components for electric and pneumatic systems.
Features include an object-oriented design which simplifies the task of configuring systems, by automatically calculating basic parameters for linked devices. A commissioning assistant makes it possible to configure a drive in just five steps, by retrieving only the essential parameters.
This simple import of the motor and cable information (and also mechanical information if a Festo actuator is used) enables automated creation of the control parameters, saving time and effort.
In addition, more advanced editing is made possible via the expert view. Fast and clear diagnostics are also available, with access to message history saved in the device, and a special trace function with which signal curves in the device can be recorded at high frequency and shown graphically.
Motion Control
Above can be seen a diagram of the statuses and status transitions of the internal finite state machine (FSM), which gives an idea of some of the functions provided by the servo drive.
Modes of operation are listed in the table above.
For comprehensive details, including the parameters supported for the different fieldbuses etc., see the Software, Function, Fieldbus, Device profile Manual (CMMT-ST-SW-EN).
Safety Features
The CMMT-ST servo drive integrates the following safety-related features:
- Safe torque off (STO)
- Safe stop 1 time controlled (SS1-t) with use of a suitable external safety relay unit and appropriate servo drive circuitry
- Diagnostic contact STA for feedback of the active safety sub-function STO
The STO and SS1-t functions are implemented according to EN 61800-5-2.
The STO function is used when the power supply to the motor needs to be switched off safely in the application, but there are no further requirements for a targeted standstill of the drive.
The SS1-t function is used when the motor needs to be braked and the power supply to the motor then has to be safely switched off in the application, but there are no further requirements for a targeted standstill of the drive.
SS1-t wiring is similar to as shown above for the STO function, with the addition of an emergency stop request (either directly by wiring CTRL-EN or indirectly via another functional controller) so that the braking ramp can be activated by the safety relay unit.
For further details, see the Safety sub-function manual (CMMT-ST-C8-1C-MP-S0-EN).
Final Words
The CMMT-ST is a smart DC servo drive which packs a host of convenient features into an extremely compact form factor, with integrated support for all the leading Ethernet-based fieldbuses. The CMMT-ST Starter Kit builds on this to provide just about everything needed to quickly get up and running, evaluating the servo drive, the supporting tools and developing solutions, and requiring the addition of only a DC power supply and a laptop for device parametrisation via Automation Suite.
— Andrew Back
The Festo CMMT-ST Starter Kit will shortly be available from RS, check back soon for an update.
Also, view our featured products below.
Festo Belt Driven Linear Actuator, 300mm, 1200mm/s RS (181-6742) >
Further Information
In a recent Ask the Expert we spoke with Colin Burke within the Electrical Automation division at Festo about Connectivity Automation and find out more about Festo in our article Festo Are More Than Pneumatics Their Electrical Range is Also Pretty Impressive
For product information about Electrical Automation Solutions by Festo then go to RS.
Comments