Position tracking of a device can be a power-intensive task, especially when trying to maintain accuracy. While GPS is a highly accurate solution, it tends to fail when the device is too close to buildings or tunnels, and has a fairly high power requirement. Other options, like Inertial Measurement Unit (IMU), are less power demanding but tend to drift in accuracy over time when used alone. 

In what it refers to as its "third wave" of intelligent MEMs sensor technologies, Bosch has recently announced the BHI160BP—a lightweight, small form factor, and low power consumption position tracking sensor.

The BHI160BP features an integrated three-axis accelerometer, a three-axis gyroscope, and a programmable microcontroller that can be paired with an absolute positioning device, such as GPS, for position tracking. 

 

Image courtesy of Bosch.

 

Low-Power Position Tracking

What makes this sensor unique is that the GPS is duty power cycled—in between GPS position reporting, the other inertial sensors interpolate the current position using a Pedestrian Dead Reckoning (PDR) algorithm. This combination reduces the power requirements of an "always on" position tracking system, while maintaining near-absolute positioning. Bosch says this allows 80% less power consumption than an always-on GPS sensor. The sensor is also reliable in environments where GPS tracking may typically fail, both indoors and outdoors. 

Bosch envisions the sensor as being used in small devices such as wearables and other small devices where battery power may be limited, and in applications that require robust position tracking. Further, the sensor is also capable of withstanding mechanical stress.

The BHI160BP microcontroller also comes with other available algorithms and software to allow features such as 3D orientation and wake-up on wearing easily available. A Sensor-API and PDR-GNSS fusion library are also available to make integration easier. 

 

BHI160BP Specs

  • Dimensions: 3.0x3.0x0.95 mm3
  • Power consumption: Six typical profiles ranging from 11 μA (suspend mode) to 1.3 mA (6 degrees-of-freedom PDR)
  • Typical PDR power savings: 80%
  • Position accuracy: 10%
  • Step counting error: 5%
  • Primary host interface: I2C, 3.4M Hz

 

Image courtesy of Bosch.

 

Pedestrian Dead Reckoning (PDR)

Dead reckoning is a method of determining position using information about current speed, known distance traversed, and last known position. It has been applied and used in air navigation, sea navigation, and even among animals. On ships, compass headings and time were used to calculate position when navigating through foggy or dark waters. 

The challenge with dead reckoning in wearable or smartphone devices is that there is a complex range of motions and orientations associated with its use. Whether it a smartwatch on the wrist of a swinging arm, or a smartphone haphazardly thrown into a pocket, these present slightly more complex challenges in calculating the magnitude and orientation of movement. 

That’s where Pedestrian Dead Reckoning comes in. A variety of sensors provide information on orientation, acceleration, and inertia; algorithms can then detect movement patterns such as walking or arm swinging and separate out that information to make dead reckoning calculations. 

 

The Third Wave of MEMS Sensors

If this is the third wave of Bosch MEMS sensors, what were the other two?

Bosch perceives the evolution of its MEMS sensors as waves: 

  1. First wave: Automotive sensors in the 1990s (airbags for safety, engine management, etc.)
  2. Second wave: Consumer electronics in the late aughts, early 2010s (particularly cell phones but also including drones, etc.)
  3. Third wave: IoT, beginning in the 2010s (including smart homes, industry, etc.) 

This new sensor is part of the third wave because it's an example of what they refer to as localized intelligence.

 

A Magical Application: Bringing the Marauder’s Map to Life

For those not familiar with the fantasy world of Harry Potter, the Marauder's Map is a map that can display the exact location of individuals inside Hogwarts castle. While the Marauder's Map is powered by magic in the novels, in real life, precisely tracking the position of individuals within the stone walls of a castle would pose challenges due to poor GPS reception. 

Bosch explores the possibility of bringing the Marauder's Map to life using the BHI160BP sensor: if the individuals within the castle are wearing smart watches or have smartphones with the sensor available, which then transmits its location to receivers, live tracking can be performed to show location and speed of individuals within Hogwarts castle without requiring a constant GPS fix. 

If anything should inspire you, the idea of creating magical objects using today’s technology may certainly be motivating.

 

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Comments

1 Comment


  • kcameron 2018-11-30

    Very cool sensor, but wouldn’t a compass be necessary? If you get an initial position using GPS and then move in the positive x direction according to the accelerometer, how does one determine if you have moved north, south, east or west on the globe? Unless the gyro is very accurate it doesn’t seem like there is a way to determine orientation…

    • adx 2018-12-02

      My guess is it’s something like that, fusing velocity and movement updates from the GPS, maybe a compass, and a low drift gyro. While gyros aren’t absolute indicators of direction (what is?), they are absolute indicators of rotational velocity, so if you can obtain a good zero from one (which is easier than a scaled signal) then you effectively have an absolute direction hold. Accelerometers have an extra step of integration so are an extra step removed from the idea of absolute position.