For many applications, the introduction of the brushless DC motor was a huge improvement over brushed DC motors. While brushed DC motors are some of the cheapest motor designs, they don't offer precise known movement with their high torque and high speed (with the exception of the servomotor).
The first brushless motors, such as those in early floppy drives, received another upgrade with the invention of the stepper motor. Stepper motors consist of a magnetic shaft with many teeth that line up and lock into position with surrounding copper coils. Depending on how the coils are driven, the motor can be made to move to specific steps either clockwise or counter-clockwise.
While stepper motors can provide accurate known steps they are not guaranteed for several reasons. If the motor is not driven correctly (possibly due to a glitch) then, unless there is an encoder attached to the shaft, there is no way for the system to recognize the malfunction. This problem can also occur if the motor stalls or is moved out of position by external forces. Some applications can tolerate this, but others that require precise movement, such as CNC machines, cannot. This can result in the difference between a properly machined product and one that has errors.
The next advancement in stepper motors is the addition of smart technology to have them perform these checks without the main system's knowledge. Trinamic recently announced a series of motors with just such capabilities.
Introducing the PD42-X-1670
The PD42-x-1670 series of motors are full mechatronic solutions that integrate a microcontroller, memory, power control, drivers, and encoders, to produce a state of the art smart motor with closed-looped feedback.
Designed around the industrial standard NEMA 17, the motors can operate on voltages between 1V0 and 28V DC, a peak current draw of 7.4A (5.2A RMS), have 4096 steps per revolution, use space-vector PWM for motor driving, and are all controlled with an ARM Cortex-M4 microcontroller.
Block diagram of the motor. Image courtesy Trinamic
The PD42-x-1670 uses the CAN bus protocol for interfacing and also includes two GPIO for generic use. As the motor can be configured, it also comes with inbuilt EEPROM which is used to store configuration data. The motor also includes other I/O connections that can be used for reference switches as well as enable inputs to the H-bridges.
Block diagram of the motor. Image used courtesy of Trinamic
The PD42-x-1670 range of motors are highly suitable for applications that require a closed-loop motor, which is capable of providing feedback on whether it has stepped correctly.
Applications and Implementation
The closed-loop feedback makes these motors appealing for automation applications in lab or factory settings. They also offer advantages in precision operations like manufacturing and robotics, as well as CNCs.
The motors offer TMCL or CANopen firmware options already integrated, easing implementation, and once set up the board can store parameters and run calculations independently, keeping communication traffic low.
PD42-X-1670 Features at a Glance
- Supply Voltage +24V nom. (+10V to +28V DC)
- 7.4A peak phase current (about 5.2A RMS)
- Integrated hall sensor based encoder (4096 counts per rotation)
- Field-oriented-control (FOC)
- Space-vector-PWM (SVPWM)
- Reference switch inputs (internal pull-ups)
- Enable input to power-on/-off driver H-bridges (internal pull-down)
- General purpose input (internal pull-up)
- General purpose output (Open-drain, max. 100mA)
CAN Bus Interface
- Standard CAN Bus Interface for control and configuration
- CAN bit rate of 20. . . 1000kBit/s
- TMCL-based protocol with TMCL firmware option
- CANopen protocol with DS402 device profile with CANopen firmware option