BLDC Gear Motors for Automated Roller Shades

Overview

This particular project was for the next generation of a series of remote control blinds. Our customer is one of the leaders in high-end home automation systems. They were looking to create an automated roller shade system that would fit universally into a series of their smart shades. This included various sizes and materials for both the commercial and residential markets. Due to the extensive collection they would need two different 24VDC brushless planetary gear motors, one small option and one larger option. This would ensure that the motorized portion of the shade would operate their entire range of window treatment solutions. This customer focused on premium home automation products, therefore our motor solution had to meet the same quality standards.

Challenge

Due to the nature of the overall shade construction and proprietary design, there were a few obstacles to overcome on the motor design side. The first challenge was determining the optimal BLDC gear motor sizes that would be versatile and powerful enough to operate their product line from top to bottom. We needed to provide two gear motors, one small option and one large option based on the specifications our customer provided us with. Since this was a retrofit into an existing design, we were presented with very limited housing space for our motor.

The next hurdle was their need for a custom output shaft on the motor gearbox to integrate with their drive-train components and additional gearing.

Our biggest obstacle was the audible noise requirement that our customer presented to us. The entire gear motor assembly and the additional drive-train components within the roller shade housing had to be quiet in order to not disturb the user in the room. This is a requirement for all of their premium line of products, and we would need to uphold those standards.

The customer also already had a custom BLDC motor driver designed and implemented. We had to make sure our motor would not require any hardware and firmware re-designs on their end. We matched the internal pole count, timing, phases, and connector with the driver to guarantee an effortless integration.

Solution

We presented our customer with two different BLDC planetary gear motor solutions. The smaller option is 22mm in diameter and the larger is 42mm in diameter. By using each of these brushless planetary gear motors, the customer is capable of retrofitting their entire line of premium roller shades. ISL Products delivered both with low audible noise and high output power.

The gear motors required very different outputs in terms of speed and torque. There were several calculations that needed to be made to overcome certain systems, while taking into account additional gearing and resistance already in the system. The values ended up being just over 3 Nm of torque at 16 rpm for the 22mm motor and about 5 Nm of torque at 45 rpm for the 42mm motor.

Both gear motors had a custom inverse hex output shaft integrated into the gearbox shaft for optimal fit and torque distribution within their drive-train. Since this was a custom shaft design, we had to tool for the production version of the output shaft. During prototyping though, we were able to get creative and make the shafts by hand.

The noise requirement was the most challenging aspect of this project. BLDC motors are quiet by nature but when you add a gearbox, it reduces the speed of the motor creating torque and the by-product is noise. We decided to use a planetary gearbox because they are the most efficient and quietest while having the ability to handle the high torque required by the blinds gear train. This development took a couple attempts to finally arrive at a suitable option. We were able to adjust our gearbox gear design and material make-up to reduce the noise whilst not sacrificing torque output. We tested the finished gear motors in an anechoic chamber each time to ensure the results were accurate.