The robotic motion system involves not only the motor but also three main functional modules.
1. Real-time controller, which behaves in the following three forms.
a fast computing processor for general purpose, motion-control firmware;
Application to DSP, DSP for control;
Dedicated controller IC circuit with hardwired and built-in algorithms.
2. One or more cascaded drive layers to take the lower layer signal out of the controller output and then output the high voltage/current required to control the switching of the electronics.
3. A MOSFET (or other switching device, such as an IGBT or a bipolar transistor) that controls the current flowing to the motor windings.
The choice of a particular MOSFET depends primarily on the current and voltage required by the motor and winding. Once the MOSFET model is determined, the driver is selected. The choice of MOSFET driver is determined by the MOSFET rating; sometimes a series of boost drivers may be required, depending on the size of the MOSFET.
3 problems you may encounter when selecting a controller
Controller model selection is also very strategic and requires a decision before selecting a specific vendor and model. There are many trade-offs when choosing whether to use a general-purpose processor for motor control, an FPGA with high computing power, or a dedicated control IC circuit (usually from a specific motor control supplier). Designers need to consider factors including:
What kind of complexity control algorithm do you need, and how many I/O ports?
Who provides the control algorithm and code: Is it an IC supplier, a third-party partner, or an unrelated third-party developer? How do they confirm and verify the performance of the motor and its applications?
How much user programming skills do you need? Even a dedicated controller that does not require programming will require the user to select the algorithm type and closed-loop control mode.
(position, speed or acceleration) and some operating parameters need to be set.
Do motors and applications have unique properties to set? If the answer is yes, then choosing a programmable IC would be better. Conversely, if you don't need to modify the algorithm, in this case, it would be better to choose a dedicated IC with a hardwired, hardened algorithm than a fully programmable IC.
Does the controller need to support multiple motor types? Even with the same type, does the controller only need to support a certain size of motor in this model, or does it support a range of sizes?
What level of technical support does the supplier provide? What are their practical hands-on experience in motor development? Will they provide a specific reference design that was built and validated, including the interface circuit between the control IC and the MOSFET driver?
Are there any regulatory issues that need attention? Authorized energy efficiency assessment
(Many motor applications must now meet a variety of "green" environmental requirements). If so, does the vendor understand these issues and do their components and algorithms meet these requirements?
4 development kits show controller and interface performance
For many engineers, merging all the parts—including controllers, drivers, MOSFETs, etc. with solidified or independent algorithms—is a task that requires multiple departments to work together, one that they don’t want to “start from scratch”. task. For this reason, many vendors offer evaluation boards or even complete kits that include controllers, example algorithms, drivers, and MOSFETs. For example, the FreescaleMTRCKTSPNZVM128 three-phase sensorless PMSM kit uses sensorless motor control technology to drive three-phase BLDC or PMSM motors. The kit is designed to support rapid prototyping and evaluation using back EMF through the integrated ADC module with a microcontroller. In addition, this kit (with the MC9S12ZVML12 microcontroller) can also be configured to evaluate the operation of Hall sensors or resolvers based on sensor evaluation.
As technology advances, including through the improved implementation of motor control and sensing, new opportunities will be created, and the future of robots is also impressive. Revolutions in key areas such as sensing, control and motors will continue to influence the revolution in robotics.
