Magnetic Position Sensors Enable Fine Robot Motor Joint Control

Confidential © ams AG 2015
ams AG Robot Demo Presentation
Magnetic Position Sensors Enable
Fine Robot Motor Joint Control
Mark Donovan - Senior Product Marketing Manager
September 28–29, 2016 | San Jose, CA

Page 2
Robot Designers Challenged to Produce Fine Joint Control
Magnetic Position Sensors provide angular position data for high precision joint motor position feedback
 For fluid joint and limb movement, fine motor joint
control of robot arms, legs, waists and head is critical.
 To achieve fine joint motor control: high resolution,
high accuracy, motor position feedback sensors are
essential.
 Position sensors need to be fast, small, and co-located
with joint motors.
 Reliable and inexpensive.
 Energy efficiency, reduced weight and reduced wiring
are also key robot design goals.

Page 3
 Contactless Rotary magnetic position sensors (POS)
are ideal for providing robot joint control feedback
 High resolution, high accuracy, low propagation
delay, angular position measurements
 Offer small footprints, and are low cost
 And in the case of ams POS devices, offer stray field
immunity for ensuring reliable, accurate and safe
robot joint movement, even in magnetically noisy
environments.
 Please see our stray field demonstrator
Magnetic Rotary Magnetic Sensors Rise to the Challenge
Magnetic Position Sensors provide angular position data for high precision joint motor position feedback

Page 4
External magnetic stray fields
(1) An external magnetic field
is present near the sensors
(3) The offset does not influence the
differential signal
(2) The external magnetic field generates
an offset on all sensors.
(4) External magnetic fields
do not influence the angle






=
)cos(*ˆ
)sin(*ˆ
arctan
a
a
a
a
a
)tan(
)cos(*ˆ
)sin(*ˆ
a
a
a
=
a
a

Page 5
How Magnetic Position Sensor Works in a Robot Joint
Joint Motor Position Sensor System Comprised of Magnetic Position Sensor and Target Magnet
Robot Joint Motor
Robot CPU
 Small diametric target puck magnet is mounted at the end
of the joint’s rotating motor shaft.
 Magnetic position sensor IC is placed directly over the
magnet with a small air gap separating the magnet and IC.
 Hall elements inside the sensor IC measure the magnetic
field generated by the target magnet
 A Cordic DSP, internal to the position sensor IC, transforms
the raw magnetic field measurement into a single angle
measurement.
 The POS sensor outputs the angle measurement over a
digital and/or analog interface(s) to the robot CPU.

Page 6
Benefits of Magnetic Position Sensors in Robots
Advanced Magnetic Position Sensors in Robot Joint Motor Control Applications
Superior durability through contactless “system-on-chip” solution
 No wear
 High reliability
 Insensitive to humidity, dust, dirt, etc.
Lower Systems Cost
 Small Surface Mount/Thru-hole IC
 Wide mechanical tolerance of shaft variations for reduced
manufacturing costs
 End-of-Line Sensor Programming for lower production costs
High Accuracy
 Rotary position error accuracy of < ±1.0o

Page 7
Benefits of Magnetic Position Sensors (Cont.)
Advanced Magnetic Position Sensors in Robot Joint Motor Control Applications
Low Power Consumption
 Normal operation 10 - 15mamps
 Low Power modes  μamps
Require minimal space
 Small Surface Mount/Thru-hole IC
Increased safety via improved accuracy and on-sensor
diagnostics
 Enabler for safety critical collaborative robot applications

Page 8
Magnetic Position Sensors in Robot Servos
Magnetic Position Sensors Replace the Traditional Potentiometer Found in Servos
 Servos, commonly used in robot joints, typically
employ potentiometers for providing motor
feedback information
 Potentiometers:
 Are not very accurate
 Wear out
 Produce electrical noise
 POS devices:
 Higher angle accuracy measurements
 Contactless, so they don’t wear out
 Do not produce electrical noise
 POS in industrial robots enable:
 Improved motor position feedback and control
 Improved safety

Page 9
Stray Field Immunity
 Robustness against unwanted external magnetic stray fields
 Reduced BOM - eliminates the need for shielding
 Guaranteed safety, reliability and durability through contactless “system-
on-chip” solution
Improved Accuracy over Lower and Wider Target Magnetic Field Levels
 < ±1.0o error accuracy over Temp for Rotary Position
 Wide Operating Magnetic Field Range (5mT to 90mT)
 Elimination of angle measurement lag at high RPM
 Dynamic Angle Error Compensation (DAEC)
Redundancy
 Dual Stacked die packaging
 Zero-defect philosophy/culture
Increased Functionality
 Low Power Modes (μamps)
 Faster Interfaces
 Shared full-duplex single wire interfaces
Emerging Magnetic Position Sensor Trends
Advanced Magnetic Position Sensors in Robot Motor Control Applications

Page 10
Improved Accuracy - Dynamic Angle Error Compensation
Advanced Magnetic Position Sensors in High Speed Measurement Applications
Hardware Compensation integrated!
No Software needed!
External HW + SW compensation needed
MagneticPositionSensorSystem
Large lag from
angle measurement
to reporting
Moderate lag from
angle measurement
to reporting
Near zero lag from
angle measurement
to reporting
Elimination of Angle Measurement Lag and Fast Refresh Rates (1.9μs) at High RPMs

Page 11
 Magnetic Position Sensors (POS)
used extensively in consumer robot
joints for providing fine motor
feedback/control
 Motor position
 Motor commutation/control
 Here we can see a POS device and
target magnet integrated into the
ankle joint of a robot.
Magnetic Position Sensors in Robot Joint Control
Magnetic Position Sensors Provide Precise and Accurate Joint Motor Position Feedback

Page 12
Magnetic Position Sensors in Robot Joint Control (Cont.)
Magnetic Position Sensors Provide Precise and Accurate Joint Motor Position Feedback
Magnetic
Position
Sensor
Target Puck Magnet at
end of Motor Shaft
Multiple Sensors in a
single joint

Page 13
Magnetic Position Sensors in Industrial Applications
Magnetic Position Sensors, with Stray Field Immunity, are ideal for Industrial Robots
 Magnetic Position Sensors (POS) in
industrial robots enable:
 Fine motor control
 Improved safety
 POS devices supporting stray field
immunity ensure reliable and
accurate joint motor position
feedback even in magnetically
noisy environments.
 Allow Industrial Robots to perform
functions that require higher level
of arm, hand, and effector dexterity
 Electronic component assembly

Page 14
Next Generation in Industrial Robots
Flexible, Faster, Lighter and work better with humans
 Replacing resolvers and optical
encoders with high resolution
magnetic position sensor ICs
 Transitioning from single to multi-
task functions
 Teaching (rather than
programming) and lighter weight
make robot repurposing much
easier
 Increased dexterity for supporting
complex/intricate electronic
assembly
 Work more safely with humans

Page 15
Magnetic Position Sensors used in drones for:
 Payload gimbals
 Position control for payload
control/manipulators
Why Magnetic Position Sensors?
 Small form factor
 Light weight
 Consume Minimal Power
 Highly accurate
 Operate in harsh environments
Magnetic Position Sensors Deployed in Drone’s
Magnetic Position sensors enabling Improved Payload Capacity and Performance, e.g. Camera stability

Page 16
What Comes Next?
The Future in Magnetic Position Sensors for Robots
 Future Magnetic Position Sensor ICs to follow will have enhanced features:
 Lower unit costs
 Ultra Low power
 Smaller packages
 Higher Accuracy
 Lower Latency

Page 17
RBR Game Changer Award 2015
Robotics Business Review
http://www.roboticsbusinessreview.com/article/as5048/

Thank you!
Please visit us at www.ams.com
Please visit our landing page
http://www.ams.com/Magnetic-Position-Sensors

Magnetic Position Sensors Enable Fine Robot Motor Joint Control

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Magnetic Position Sensors Enable Fine Robot Motor Joint Control