Editor’s Note: ams AG will be speaking about and demonstrating its next-generation magnetic position sensors at RoboBusiness 2017, which will be held in Santa Clara, Calif., on Sept. 27 and 28.
Over the past couple of years a new set of end markets and applications have begun to drive the requirements and set the standards for higher performing position sensors. This has been particularly evident with magnetic position sensors, where suppliers of these types of sensors have responded to the siren calls and have begun to introduce new products specifically tailored for the rapidly growing robot and drone markets.
New magnetic position sensors are smarter and offer higher resolution and accuracy, are smaller and lighter, and consume dramatically less power than their predecessors. This article will explore:
- History of magnetic position sensors and how and what end markets they’ve traditionally served
- New features and performances being introduced in today’s next-generation devices
- Use cases in the robot and drone spaces for these new and innovative magnetic position sensors.
How magnetic position sensors are used
Hall-based magnetic position sensors have been around for a long time, but they are still increasingly being used today in automotive, consumer and industrial applications with the continued electrification of these end markets. In automotive, for example, magnetic positions sensors are used today for such vehicle sub-systems as steering, braking, transmission, shifter, chassis ride height, pedal, fuel leveling sensing, etc. And the rush for autonomous driving vehicles is only accelerating their use.
In the consumer space, they are widely used for detecting door position in white goods appliances. And in the industrial market, they are used for providing actuator, lever and joystick position feedback for control systems and industrial robots. Moreover, across all markets, they are heavily used for aiding in motor control.
The main reasons why magnetic position sensors are so widely used is that they can be realized in low-cost CMOS semiconductor technology and provide accurate, repeatable and reliable position measurements in the harshest of environments. Magnetic position sensors are immune to dust, dirt, grime, and liquids, and can work in high temperatures and humidity levels. Some suppliers, such as ams AG, even offer magnetic position sensors that are immune to magnetic stray fields.
Traditionally, CMOS magnetic position sensors have been packaged in various common surface mount and single in-line thru-hole IC packages, and for most of the applications just mentioned this type of packaging has been adequately small enough. Similarly, CMOS magnetic position sensors typically consume power in the 10s of amps of current. Again, tolerable power consumption levels for the conventional automotive, industrial and consumer markets.
No longer cutting it
However, with the rapid electrification of automobiles, new IOT connected consumer products being announced with ever-growing frequency, and industrial equipment and factories becoming increasingly more efficient and smarter through the use of robots and artificial intelligence, the magnetic position sensors of yesterday are no longer cutting it. They are often viewed by today’s designers as too large in both their physical size and power consumption requirements, and their accuracy performance inadequate for their systems’ performance goals.
This same view of conventional magnetic position sensors is shared by today’s robot design engineers who are working to produce new robots for end markets such as light industrial, medical, and space exploration. In all three end markets robot designers need ultra-small and very low power magnetic position sensors for producing very small high precision robotic arms. Robot arms that will be used for doing such intricate tasks as assembling electronic components, performing various types of laparoscopic surgery, and for picking up small rock and sediment samples on distant planets.
Drones need small magnetic position sensors
Similarly in the rapidly growing drone market, where size, weight and low power consumption are critical requirements for enabling longer mission flights, the need for ultra-small and very low power magnetic position sensors is vital in the area of the drones’ camera gimbals. Magnetic position sensors are used in a drone’s camera gimball for providing commutation feedback to the brushless DC gimbal motors, and for providing gear angular position feedback in three dimensions. Without these magnetic position sensors camera stability for providing stunning video photography would not be achievable.
Fortunately, magnetic position sensor suppliers are responding to the needs of their customers and these new end markets with a new generation of magnetic position sensors. Magnetic position sensors that are packaged in ultra-small packages, including Wafer Level Chip Scale Packaging, WLCSP, where the package is nearly the same size as the sensor die itself, and position sensors that have the ability to automatically go into low power modes to reduce their overall power consumption.
ams AG, for example, offers two devices that are meeting the needs of these new requirements. The AS5510 linear position sensor is offered in a WLCSP with package dimensions of just 1.46mmx 1.0mmx0.6mm, and has a low power mode that consumes only 25µA of current. Similarly, its AS5055A, with 12-bit resolution, is offered in a small QFN-16 package (4.9mmx 6.0mmx1.75mm) and has a low power mode that draws only 3µA of current.
Due to these features, the AS5055A is used extensively in motor control systems that require a very small volume and ultra-low power. It is currently empolyed in a variety of end-market applications for motor control, including robots for industrial and consumer applications and interplanetary space exploration. ams also offers several magnetic position sensors in System in Package (SiP) packaging solutions, where the sensor and associated decoupling caps are integrated into the same package, enabling PCB-less designs for achieving lower system costs and smaller form-factor solutions.
ams has also recently begun sampling its newest magnetic angle position sensor, the AS5600L. It provides 12 bits of output resolution, with a maximum INL (Integral Non-Linearity) error of just 1o degree over its full operating temperature range of -40 to125oC, is offered in a WLCSP (2.07mm x 2.63mmx0.6mm) package, and consumes only 1.5mA of current in its automatic low power mode. Below are two sample simulaton plots of the AS5600L’s INL error at a 1.5mm airgap (Z), and with up to ±1mm of X/Y misalignment between the target magnet and the sensor itself. As can be observed in the plots, with zero X/Y misalignment an INL error of < ±0.5o is achievable for both target magnets. With an airgap < 1.5mm even lower INL errors can be obtained.
These type of low INL errors, or accuracy results, along with low noise and very low power consumption over wide temperature ranges and target magnetic flux fields, are enabling ultra-small Hall Effect based magnetic position sensors like the AS5600L to meet the performance and space requirements of today’s robot and drone design engineers. Moreover, they are doing so at competitive cost advantages over competing position sensor technologies.
Robot arms with more dexterity
Robot designers developing new robots for various end markets including, medical, light industrial, and geological and space exploration, are taking advantage of these next generation magnetic position sensors to produce robots with smaller and higher dexterity limbs. Small robot arms and limbs that can more quickly and precisely pick up and move objects for applications such as: performing light industrial electronic assembly tasks, enabling robotic laproscopic surgery, and even for picking up small soil samples on distant planets. Specifically, they are using the magnetic position sensors for providing joint motor commutation and gear position feedback.
To realize these smaller robot arms mechatronic design engineers are utilizing flex printed circuit boards to mount these small magnetic sensor ICs onto, and for routing their power and data signals back to a main controller in the main body of the robot. See Figure 2.0 below.
In the drone space it is a similar story with the use of next generation magnetic position sensors. Drone designers are developing new 3-axis camera gimbals that use many of the same technologies in smart phones to provide camera stability for ensuring gorgeous cinematography. However, it is the use of ultra-small and low power magnetic position sensors that play a pivotal role and providing 3-axis position feedback of the camera gimbals’ brushless DC motors and gears to ensure that the camera remains constantly level and vibration-free while in flight and filming. See Figure 3.0.
Creating future applications
To conclude, today’s next generation magnetic position senor ICs, with their high accuracy and small size and power consumption, are enabling today’s electrical and mechanical design engineers to produce new and highly functional robots and drones that can serve many new markets and applications.
In the not-so-distant future, we can expect to see smaller medical robot arms literally penetrating and maneuvering around inside the human body to remove tumors and perform other surgeries. In the industrial robot market, we can expect to see the use of smart and lite-manufacturing robots to perform more intricate tasks such as electronic assembly.
And in the drone space, we can continue to see the evolution and improvement of camera and payload gimbals to support even higher resolution photography and perform more accurate 2D and 3D mapping.Read More