Robots must be equipped with multiple motors in order to move the robot body or the robot's arms and limbs, with brushless DC (BLDC) motors as the mainstay. In order to drive brushless motors efficiently, appropriate brushless motor drivers must be selected. This paper introduces the characteristics and selection points of brushless motors and drivers, as well as the product characteristics of brushless motor drivers launched by onsemi.
Brushless motors that are more efficient than brushed motors
Brushless motors and brushed motors are two different types of motors. Their main difference is whether there is a brush structure inside them. There is a pair of brushes inside the brushed motor in contact with the rotating rotor to transfer electrical energy to the rotor through the brush, thereby generating rotation. However, brushless motors do not require brushes to control the direction of current through internal electronic controllers, such as transistors, and apply electromagnetic force directly to the magnets in the rotor, thereby generating rotation.
Since brushless motors do not have brushes, friction and wear can be reduced during high-speed operation and they are therefore usually more efficient than brushed motors. In addition, brushless motors can control speed and torque more accurately and are therefore more suitable for applications requiring high precision motion control.
In addition, more maintenance is required as brushed motors have brushes that are prone to wear and tear and thus require regular replacement. Brushless motors do not require such maintenance and are therefore more user-friendly. Usually, however, brushless motors are more expensive than brushed motors, but the cost of brushless motors has become increasingly close to brushed motors as brushless motor technology advances and market competition intensifies.
Since brushless motors use electronic controllers to manage magnetic fields and current, they are more efficient than conventional brushed motors and can provide high torque at low speeds, which makes them suitable for power-starting applications such as power tools and robots. Because brushless motors can operate at high speed, this makes them suitable for applications that require high-speed motion, such as unmanned aerial vehicles and electric vehicles.
Furthermore, since brushless motors use electronic controllers rather than mechanical parts such as brushes and collectors, they are more durable than conventional brushed motors, and since the operation of brushless motors is accomplished by adjusting current through electronic controllers rather than through mechanical friction and contact, they are usually quieter than conventional brushed motors. Because brushless motors have better performance and longer life than conventional brushed motors, they are widely used in a variety of applications, including industrial automation, household appliances, power tools, unmanned aerial vehicles, electric vehicles, etc.
Tips for selecting brushless motors
When selecting brushless motors, you first need to determine what types of brushless motors are required for your application, such as whether you need high torque, high speed, or both, in order to provide the best performance for your application. In addition, correct brushless motor voltage and power must be selected based on power supply and application requirements. In general, the higher the input voltage and power, the better the performance of the brushless motors, but the corresponding costs will increase.
On the other hand, you need to determine the range of speed required for the application and select brushless motors that can provide the desired speed. The efficiency of brushless motors is important because efficient brushless motors can save energy and reduce operating costs.Therefore, selecting an efficient brushless motor can bring better efficiency and economic benefits to your application. There is also a need to select brushless motors with good durability and life expectancy, which will minimize repairs and replacements and reduce operating costs. Finally, a reliable brand and a high-quality brushless motor need to be selected to ensure that your application can operate steadily for a long time and maximize your benefits.
Key points for selection of brushless motor drivers
Once a brushless motor is selected, the brushless motor driver must be selected. First, you need to determine the type of brushless motor you will use, such as a DC brushless motor, stepper brushless motor, etc., and select the appropriate brushless motor driver. Then you nleed to select a brushless motor driver based on the current and voltage of the brushless motor you will use. Normally, the maximum current and voltage of brushless motor drivers needs to be greater than the rated current and voltage of the brushless motors.
In addition, brushless motor drivers are controlled in various ways, such as PWM control, pulse direction control, etc. Therefore, it is necessary to select the control method suitable for your application, and then determine whether your application requires speed control features, and if so, select brushless motor drivers that support speed control. Brushless motor drivers usually have protective features such as overcurrent protection and overheat protection. You need to determine whether these protective features are required for your application to select appropriate brushless motor drivers. Of course, trustworthy and high-quality brushless motor drivers will help your application run steadily and ensure the overall system operates efficiently.
Easy-to-use brushless motor drivers
For high-precision robotic applications, onsemi launched the NCD83591 brushless motor driver, a three-phase 60V gate driver for motor control applications. The NCD83591 is fairly easy to use, has a high gain-bandwidth current sense amplifier, making it ideal for trapezoidal motor control applications. It includes a configurable FET constant gate drive source current of 5 to 250mA on the high side, which is a 2 times proportional sink current on the low side. The high side gate drive is enabled with an embedded charge pump that allows for DC static drive and is tolerant to -12V DC.
The NCD83591 supports an internally generated gate driver power supply voltage with a wide operating voltage range that makes the device well suited for industrial and commercial applications ranging from 5 V (minimum) to 60 V (maximum) with tolerances ranging from 4 V to 70 V. The gate driver is packaged in a small footprint QFN28 (4×4) and with a high level of integration, making it ideal to optimize the overall BOM cost.
The NCD83591 is a 60V three-phase gate driver with an absMax of 70V, embedded current sense amplifier, externally configurable with an embedded 10MHz GBW general-purpose amplifier, integrated charge pump for high side gate driver, and 16 settings by input level to VDRV pins for gate sensing for cross conduction protection and optimized dead time.
The NCD83591 has the capability to detect current, with embedded charge pump function allowing DC static drive, supports strong hold-off current preventing self-turn-on, internal gate pull-down to GND during loss of VDD (core) power, under voltage lock out on VM, VGL, and VGH−VM, features 5V/3.3V compatible 6 input control plus enable, and up to 30 kHz motor PWM with individual six gate control mode, 4kV HBM and 1kV CDM ESD protection, and is a Pb-free device. onsemi also launched an NCD83591AS-GEVB evaluation board in support of NCD83591 to accelerate product development.
The NCD83591 can be used in power equipment, building and industrial automation, mobility, robotics, etc. Common end products include power tools, outdoor power equipment, factory automation, building management, electric bicycles, electric scooters, hoverboards, cobots, automated guided vehicles, autonomous mobile robots, and unmanned aerial vehicles.
Conclusion
The operating characteristics of brushless motors are fairly suitable for robotic applications and can efficiently drive various robotic movements. Therefore, it is even more important to select suitable brushless motors and drivers. Brushless motor drivers introduced by onsemi for robotic applications, featuring high integration, efficiency, stability, and low cost will be ideal for robotic applications.