Optical Flow Sensor for Mobile Robots

Roboteq’s FLW Family of Optical Flow Sensors are high-resolution sensors especially designed for accurate contactless X-Y motion and rotation sensing over a surface. The sensor works similarly to an optical mouse, but with higher resolution, accuracy and at greater distance from the reference surface.

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Improving Dead Reckoning Robot Navigation

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Knowing how much the robot has moved and rotated will greatly help the precision of the robot’s positioning along its expected travel path. Because it is more precise and dependable than wheel-mounted encoders, it greatly supplements laser range finders and cameras in region with little distinctive visual features.

Measure Travel with Precision

The sensor uses an embedded infrared laser illuminator and camera that is pointed to the floor and measures the displacement distance and speed along the X and Y axis. It works by comparing images at each frame. Distance is measured with 0.1mm resolution from a height of 10 to 30mm with excellent accuracy.

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Works on any hard surface

The sensor works on practically all types of hard surfaces, including title, wood or concrete. It’s laser technology will recognize features on light, dark and even glossy material at speeds up to 1.0 or 2.0m/s depending on the model.

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Single or Tipple Laser Version with IMU

Single Laser sensor provide an economical solution when only X-Y translation motion detection is required. The Triple Laser version also measures angular rotation. The extra lasers also improve reliability through redundancy, the sensors incorporate a 9-degree of freedom sensor (gyroscope, accelerometer and magnetometer). A fusion algorithm blends the info from the optical sensor and the IMU to improve accuracy and compensate temporary data loss from any of the sensing devices.

 

flw200 flw100
 FLW100

1 laser, 1 IMUs, 1ms/max, 20-40mm range 

FLW200

3 lasers, 2 IMUs, 2ms/max, 10-20mm range

A Unique Solution for Functional Safety

Roboteq’s Flow Sensors can be used to monitor the Robot’s motion and verify that is remains within the expected safe range. For example, the sensor can detect and report if the robot is moving faster or slower than expected or spinning out of control. The sensor’s digital outputs can be used to cut the power to the motor controller or activate the Safe Torque Off signals.

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Example SS1 Safety Stop Implementation.

  1. Stop command issued to Motor Controller and Flow Sensor
  2. Sensor checks if Robot Slows Down and Stops
  3. Flow Sensor activates Motor Controller’s STO pin if not

Multiple Interface – Connect to Anything

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The Flow Sensors have an 8-pin M12 industrial connector for its power supply, communication and I/O connections. The communication interface can be configured as CANbus, RS232 or serial TTL. Four I/O pins can be configured as Dual Quadrature Encoder outputs, as PWM output, or as user I/O. The FLW can be connected to a PC via its USB port for configuration and monitoring.

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So Smart, You'd Think it is a Computer