Moog Animatics’ Knowledge Base
This is your online source for all information needed to become a motion control expert.
From understanding SmartMotor™ torque curves and motor sizing to cable configurations and OEM Dynamics linear actuator training videos, Moog Animatics’ Knowledge Base exists to support our customers in any and every question or concern they may have and provide every explanation before you even pick up the phone.
SmartMotor Knowledge Base
|1. SmartMotor™ 101||2. Sizing the SmartMotor™|
|3. Fieldbus Options||4. Brake Options|
|5. Gearheads||6. CAD Drawings Download|
|1. About OEM Dynamics||2. Multi-Axis Configurations|
|3. Understanding Actuator Loading||4. Reading Thrust Curves|
|5. Control System Overview||6. Modes of Operation|
|7. Advanced Drive Capabilities||8. CAD Drawings Download|
Each SmartMotor has a primary RS232 serial port and a secondary RS485 port by re-assignment of ports E and F of the 7 I/O points. Up to 100 SmartMotor servos may be separately addressed and are identifiable on either RS232 or RS485.
The most common and cost effective solution is typically RS232 serial communications. Under this structure, each motor is placed in an electrical serial connection such that the transmit line of one motor is connected to the receive line of the next. Each motor will be set to "echo" the incoming data to the next motor down with approximately 1 millisecond propagation delay. There is no signal integrity loss from one motor to the next, which results in highly reliable communications.
Here's a roadmap to motor connectivity which shows the physical layout of
how cables are used including power, communications, and I/O interconnection.
|RS-232 and Power||CBLPWRCOM2-xM||Power and communications cable with flying leads or in conjuction with DIN-RS232 8 channel isolated communications board|
|CBLSM1-xM||Power and communications cable with DB-9 serial connector and power supply connector that fits our enclosed power supplies|
|CBLSM1-DEMO||Testing cable used with our PWR116 "laptop" type power supply|
|CBLSM1-x-y-z||Custom length multi-drop RS-232 daisy chain cable|
|RS-485 and Power||RS485-ISO||Converts primary RS-232 to isolated RS-485 (Note: uses Port G I/O pin)|
|CBLSM2-x-y-z||Custom multi drop isolated RS-485 (multiple RS485-ISO adapters)|
|Interfacing with I/O Devices||CBLIO5V-xM||Direct connection to 5VTTL I/O|
|CBLIO5V-xM via OPTO2||24VDC DC isolation and conversion of 5V signals|
|CBLIO5V-xM via DINIO7||Motor breakout board to industry standard OPTO relays|
|CBLIo-ISO1-xM||Isolated 24VDC logic conversion cable|
Each SmartMotor is operated from 24V to 48VDC. Some of the larger SmartMotor servos can draw high current.
It is highly recommended to use heavy gauge wire to connect the larger motors. As a result, the "Add-A-Motor" is recommended for the 17 and 23 frames series only.
How to Choose Power Supplies
Which is better, Linear or Switcher Supplies?
Since servo motors are inductive they may run highly dynamic motion profiles. As a result, their current demand can vary widely. Surge currents from stand-still to maximum load may be extremely high, yet steady state curret demand over time may be relatively mild. As a result, proper care should be taken when selecting power supplies.
Moog Animatics offers two basic types of power supplies.
The below chart gives a brief comparison of the two types of supplies.
|AC Input||Field selectable
|Power Factor Corrected||NO||Yes|
|Relative Size||Big and bulky||Lightweight|
|Cooling||Ambient Convection||Fan cooled|
|Voltage Regulation||15% Drop over range||0%, fixed8|
but not typically
|In most cases,
1See Shunt Section for more information!
Voltage Drop Comparison
As seen in the graph to the right, Linear (Unregulated) suppllies can handle large surge current loads. This is because linear supplies typlically contain large output capcitors to handle those surges well.
Voltage regulations: Switchers are highly regulated supplies. They will maintain fixed voltage until they reach maximum load and then will "crowbar" to zero volts to protect the output stages. Linear supplies will slowly drop in output voltage while supplying more and more current.
This is the most funamental difference between switchers and unregulated supplies.
Even though a switcher cannot handle the higher current surges, if it can ouput as much current as you would expect for a given servo application, then they will actually help the servo accelerate much faster because system voltage will be maintained at maximum level.
However, if your servo application requires surge currents in excess of 50 Amps or more, the switchers may not be cost effective. Getting 50 amps from a Moog Animatics 20 Amp supply is easy. Getting 50 Amps from Moog Animatics switchers would require placing multiple units in parallel, so it may not be cost effective to do so.
Intro to Shunts
Moog Animatics offers several shunt options for use with DC input servo motors.
Shunts are needed to protect the servo controller and drive stages from over voltage.
Over voltage sources originate from the following:
- Back EMF due to back driving the motors
- Sudden or hard decelerations
- Hard stop crashes (immediate deceleration to zero speed)
- Vertical load drops
The shunts actually add an additional load to the DC bus automatically when voltage exceeds the trigger level by connecting large load resistors across the bus. Trigger voltage is typically 49.5VDC. As a result, the shunts will work with any of the supplies we offer.
The switcher supplies have an adjustable output trim pot. If used with our shunts, the output voltage MUST BE adjusted to <=48vdc to insure the shunts do not stay gated on.
- Shunts cannot be placed in parallel with each other to increase capacity. The shunt with the slightly lower trigger voltage will trigger first while the other shunt never triggers at all. Please consult factory for information on how to deal with larger shunt requirements.
- Shunts should always be placed between the motor input and any disconnect or e-stop relay to insure protection of the motor when power is not applied or e-stop relay contacts are open.
The Real story about Back EMF:
Generally speaking, back EMF is the voltage generated in a motor when it spins. This voltage is typically propotional to speed. However, this is a general rule. The truth is that the back EMF voltage is proportional to the rate of change of magnetic flux in the windings of the stator. As a result, consttant speeds produce contant and predictable voltages. However, sudden changes due to decelerations or hard stop crashes cause an immediate change in magnetic flux or even a total instantaneous collapse. As a result, voltages can go 5 to 10 times higher than spinning the motor at its maximum speed.
For this reason alone, it is highly recommended to use a shunt in all vertical load applications or any case where the motors could be stopped quickly or back driven suddently.
We offer both open frame and enclosed shunts in 100Watt and 200Watt capacities. The shuns are all automatic and get their power from the DC bus they are attached to. They simply need to be placed in parallel with the DC bus.