January 03, 2020 by Sam Holland
The AS5715 inductive sensor, which is the first inductive position sensor for automotive, industrial, and high-speed electric motors, provides size, cost and weight savings unlike the resolvers commonly used in cars today.
The AS5715’s easy adaptation, flexibility, and low system costs make it a suitable replacement for the resolver, and it can be used for both on-axis and off-axis applications.
ams claims this is the industry’s first inductive position sensor that will be made available as a standard product. Besides maximizing torque, the sensor IC can reduce torque ripple and increase efficiency in high-speed motors. This is credited to highly precise, low-latency position measurements.
In fact, according to ams, a position sensor, using an AS5715 IC, can manage ±0.3° accuracy at up to 100,000 rpm rotation speeds, even on four-pole PMSMs (permanent magnet synchronous motors). The rotor position sensing capabilities are top-notch, and provide significant savings in terms of cost, size, and weight.
Highly configurable: it can be used in on-axis (end-of-shaft) and off-axis (side-of-shaft or through shaft) topologies and with a variety of multi-pole-pair motor
The measurement outputs are easy to use: Its method of operation resembles that of a resolver as it has two pairs of differential analog SIN/COS output.
Flexible PCB design
Low propagation delay
Less than 1.0° angular accuracy
Ability to sense motors with low and high pole-pair counts without losing resolution
AEC-Q100 Grade 0 qualified
Adaptable coil and sensor layout
Can handle motors up to 480 000 rpm
ISO 26262 compliant
The AS5715 is mounted onto the AS5715 reference board, which has peripheral components, sensors and all other necessary external components soldered onto the PCB. The connector needs to be populated with a 6-pin plug strip and is required for power supply as well as I2C and analog output interfaces. Where the 6-pin plug is used, it must be soldered on the board.
To enable communication over the I2C-interface, ensure you connect the PCB to an external microcontroller or the production programmer of SD4Y.
First, assemble the reference board with the ceramic spacer, then put the target on the spacer and connect the board to supply. After powering up the board, the sensor should be in functional mode with analog sine and cosine signals available at the connector.
IncOder 37-mm inductive angle encoder. Image Credit: Celera Motion.
The most viable alternative to traditional resolvers are the Zettlex Inductive IncOders, that utilise high-reliability inductive angle encoder technology. Zettlex IncOders use the same fundamental physics as resolvers and exhibit the same high levels of safety assurance, robustness, and reliability.
These devices use a printed circuit board construction and don’t require external resolver signal generation and processing electronics. The Zettlex Inductive Encoder technology offers high levels of accuracy to comparable size resolvers. Their patented technology enables them compact form, low inertia, low mass, and high accuracy without high precision installation.
Reference board for AS5715. Image Credit: ams.
The main application for the AS5715 is automotive electrification. In fact, the commercialization of this inductive sensor semiconductor tech should mark an important milestone in the process of electrifying automotive systems in electric and hybrid-electric vehicles–at least this is what ams hopes for.
Several automotive trends–like the transition from brushless DC motors to PMSMs–trigger the need for improved position measurements which the AS5715 can provide. Moreover, governments, in response to the climate crisis, are championing low fuel consumption in vehicles, which is pushing carmakers to install motors that are efficiently controlled.
This high-performance off-axis inductive position sensor can also be used in electric window lifts, HVAC pumps, and EPS motor drive.
Launching the AS5715 is a significant milestone in providing tech for greener and smarter cars. Motors built using this sensor will be smaller and lighter, and deliver a more efficient and powerful output. Coupled with other advantages like cost savings, ease of adaptability, and flexibility, these devices provide the perfect replacement for the larger and more expensive resolvers used in modern cars.
