Lidar - Revision history

Luke at 19:53, 22 August 2025

2025-08-22T19:53:33Z

Tfolsom: /* Process */

2019-06-28T18:35:50Z

‎Process

Tfolsom at 18:34, 28 June 2019

2019-06-28T18:34:16Z

JosephBreithaupt: /* Software */

2019-06-06T21:04:30Z

‎Software

JosephBreithaupt at 21:02, 6 June 2019

2019-06-06T21:02:04Z

JosephBreithaupt: /* Hardware */

2019-06-06T20:00:50Z

‎Hardware

JosephBreithaupt at 19:57, 6 June 2019

2019-06-06T19:57:35Z

JosephBreithaupt: JosephBreithaupt moved page ScanseSweep to Lidar: this is our lidar page discussing hardware and software

2019-06-06T19:24:48Z

JosephBreithaupt moved page ScanseSweep to Lidar: this is our lidar page discussing hardware and software

JosephBreithaupt: Created page with " = Scanse Sweep = The Scanse Sweep is a lidar sensor. Its head spins around multiple times per second, and collects information about its lateral surroundings. The spin spee..."

2019-05-20T02:35:38Z

Created page with " = Scanse Sweep = The Scanse Sweep is a lidar sensor. Its head spins around multiple times per second, and collects information about its lateral surroundings. The spin spee..."

New page

= Scanse Sweep =

The Scanse Sweep is a lidar sensor. Its head spins around multiple times per second, and collects information about its lateral surroundings. The spin speed and sampling rate can be changed.

It sends readings over a serial connection, each of which includes the angle, distance, signal strength, and other information.

Blasé Johnson worked on the sweep in the summer of 2017. The following is from his 6/22/17 report.

= Basic Sweep Obstacle Detection Algorithm =
Goal

To use the readings from the sweep to determine if there is an obstacle present within a given distance in front of the trike, and to stop the trike if this is so.
Sweep Operation
Rotation and Speed
The Sweep rotates counterclockwise. Its rotational speed can be set to any integral value between 0 Hz and 10 Hz (number of full rotations per second).

= Sampling Rate =

The sweep obtains readings according to a given sample rate. Three distinct sample rates can be used for the Sweep:
500 – 600 Hz
750 – 800 Hz
1000 – 1075 Hz\

= Sample Data =

Each reading from the Sweep contains these data:

* A byte with sync/error bits, where the sync bit indicates whether the current reading is the first reading since the sensor last made a full rotation, one of the error bits indicates a communication error with the Lidar module, and the rest of the bits are reserved for future uses.

* The azimuth (degree of angle with starting position), transmitted as a 16-bit fixed point number, where the 12 MSBs are the integral part and the 4 LSBs are the fractional part.

* The distance from the nearest obstacle in centimeters, transmitted as a 16-bit integer.

* A value representing the signal strength, transmitted as an unsigned 8-bit integer, where 0 is the lowest strength, and 255 is the highest strength.

* A checksum, which is the remainder of the sum of the six previous bytes divided by 255.

= Math =

The trike will be expected to stop if an obstacle is detected within a certain distance from the front side of the vehicle, within the horizontal span of the trike. These distances are illustrated in Figure 1 as DISTANCE and WIDTH, respectively. 
The grey lines in Figure 1 show the distances that will be measured by the Sweep if it detects an obstacle at the line. The formula for this distance is DISTANCE/cos(AZIMUTH) .
The range of azimuths for the front side of the trike can be computed from the formula sarcsin(WIDTH/(2*DISTANCE))
and
360-arcsin(WIDTH/(2*DISTANCE))
for the right and left corners, respectively.

= Process =

Once the Sweep begins taking measurements, check the measurements whose azimuths lie within the boundaries of the front side of the trike. For each measurement within this range, determine if the distance from an obstacle in centimeters is equal to or less than DISTANCE/cos(AZIMUTH) . If so, stop the vehicle until a search of the measurements within the front boundary comes back negative, and a certain amount of time has passed since the last obstacle was detected.W

== External Links ==

[http://scanse.io/ Scanse]

-- Main.JohnsonB - 2017-11-07
* Figure 1: Distance from trike to detect obstacle & trike width: <br />
<img src="%PUBURLPATH%/%WEB%/%TOPIC%/ScanseTrike.png" alt="ScanseTrike.png" width="397" height="463" />

← Older revision		Revision as of 19:53, 22 August 2025
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	Blasé Johnson worked on the sweep in the summer of 2017. The following is from his 6/22/17 report.		Blasé Johnson worked on the sweep in the summer of 2017. The following is from his 6/22/17 report.
		+
		+	= YDLIDAR =
		+
		+	The YDLIDAR was worked on for the autonomous ATV capstone project summer of 2025 by Henry Haight. The lidar separates the data it detects and creates objects that can be used by the software. More information can be found on the GitHub page: https://github.com/elcano/Obstacles

	= Basic Sweep Obstacle Detection Algorithm =		= Basic Sweep Obstacle Detection Algorithm =

@@ Line 85: / Line 85: @@
 Once the Sweep begins taking measurements, check the measurements whose azimuths lie within the boundaries of the front side of the trike. For each measurement within this range, determine if the distance from an obstacle in centimeters is equal to or less than DISTANCE/cos(AZIMUTH) . If so, stop the vehicle until a search of the measurements within the front boundary comes back negative, and a certain amount of time has passed since the last obstacle was detected.W
-NEXT > [[ScanseSweep]]
+NEXT > [[Camera]]
 == External Links ==

← Older revision		Revision as of 18:34, 28 June 2019
Line 85:		Line 85:
	Once the Sweep begins taking measurements, check the measurements whose azimuths lie within the boundaries of the front side of the trike. For each measurement within this range, determine if the distance from an obstacle in centimeters is equal to or less than DISTANCE/cos(AZIMUTH) . If so, stop the vehicle until a search of the measurements within the front boundary comes back negative, and a certain amount of time has passed since the last obstacle was detected.W		Once the Sweep begins taking measurements, check the measurements whose azimuths lie within the boundaries of the front side of the trike. For each measurement within this range, determine if the distance from an obstacle in centimeters is equal to or less than DISTANCE/cos(AZIMUTH) . If so, stop the vehicle until a search of the measurements within the front boundary comes back negative, and a certain amount of time has passed since the last obstacle was detected.W

		+	NEXT > [[ScanseSweep]]

	== External Links ==		== External Links ==

@@ Line 21: / Line 21: @@
 = Software =
-Software on the Arduino Micro controls the Scanse Sweep. On startup, the '''setup()''' procedure resets the lidar, configures scan frequency and motor rotation frequency, waits for the motor to come up to speed, and sets the lidar to begin scanning. The '''loop()''' procedure requests the most recent complete scan reading, filters out invalid readings, and processes the signal for transmission to high level.
+Software on the Arduino Micro controls the Scanse Sweep. On startup, the '''setup()''' procedure resets the lidar, configures scan frequency and motor rotation frequency, waits for the motor to come up to speed, and configures the lidar to begin scanning. The '''loop()''' procedure requests the most recent complete scan reading, filters out invalid readings, and processes the signal for transmission to high level.
 == Filtering ==
@@ Line 33: / Line 33: @@
 == Signal processing ==
 Signal processing is required to limit bytes sent to [[HighLevel]] but still allow HighLevel to reconstruct obstacle data from the scan. At maximum sampling frequency, the lidar unit collects 1000 range readings per second. Some of these reading are filtered out. This results in tens or hundreds of readings during each pass. To reduce data bandwidth, the software uses a "max delta" value to break the scan into segments beginning and ending at points with a change in range greater than the max delta. This discards small changes in range, but detects larger changes in range that indicate obstacles. This balances the need to detect both obstacles and continuous surfaces like walls. A single straight surface is broken into several segments centered on the closest point. If obstacles are placed on front of the surface, the change in range for each obstacle produces one or more segments for each obstacle and one or more segments for each section of straight surface. How accurately this process reconstructs the field of obstacles depends on how many points are filtered out before signal processing: if obstacle data is missing, it will not begin or end a segment.
 = Scanse Sweep =

@@ Line 1: / Line 1: @@
 = Hardware =
-Scanse Sweep is a portable, rotating, horizontal-plane lidar unit. It has a maximum specified range of 40 meters and works best at ranges greater than 0.5 meter. '''Range data''' precision is 1 centimeter and range values are in centimeters. Angular resolution is user-configurable by adjusting sample rate and motor rotation frequency. Surface variables like reflectivity and environmental variables like strong illumination by sunlight limit measurement signal quality. Not every reading is good quality, leaving blind spots in the scan. '''Angle data''' precision is 0.0625 degrees and angle values are in degrees, expressed as a 16-bit fixed-point number with twelve integer bits and four fractional bits.
+Scanse Sweep is a portable, rotating, horizontal-plane lidar unit. It has a maximum specified range of 40 meters and works best at ranges greater than 0.5 meter. '''Range data''' precision is 1 centimeter and range values are in centimeters. Angular resolution is user-configurable by adjusting sample rate and motor rotation frequency. Surface variables like reflectivity and environmental variables like strong illumination by sunlight limit measurement signal quality. '''Signal quality''' is a number between 0-255, with smaller numbers indicating poorer signal quality. '''Angle data''' precision is 0.0625 degrees and angle values are in degrees, expressed as a 16-bit fixed-point number with twelve integer bits and four fractional bits.
 {| class="wikitable"
@@ Line 19: / Line 19: @@
 The Scanse Sweep lidar unit is connected to an Arduino Micro to capture and process range, angle, and signal quality data during a scan.
 = Scanse Sweep =

@@ Line 6: / Line 6: @@
 |-
 ! Angle bits
-! Angle decimal
+! Angle decimal (degrees)
 |-
 | ...0000'''0001'''
@@ Line 18: / Line 18: @@
 |}
 The Scanse Sweep lidar unit is connected to an Arduino Micro to capture and process range, angle, and signal quality data during a scan.
 = Scanse Sweep =

← Older revision	Revision as of 19:57, 6 June 2019
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	+	= Hardware =
	+
	+	Scanse Sweep is a portable, rotating, horizontal-plane lidar unit. It has a maximum specified range of 40 meters and works best at ranges greater than 0.5 meter. '''Range data''' precision is 1 centimeter and range values are in centimeters. Angular resolution is user-configurable by adjusting sample rate and motor rotation frequency. Surface variables like reflectivity and environmental variables like strong illumination by sunlight limit measurement signal quality. Not every reading is good quality, leaving blind spots in the scan. '''Angle data''' precision is 0.0625 degrees and angle values are in degrees, expressed as a 16-bit fixed-point number with twelve integer bits and four fractional bits.
	+
	+	{\| class="wikitable"
	+	\|-
	+	! Angle bits
	+	! Angle decimal
	+	\|-
	+	\| ...0000'''0001'''
	+	\| 0.0625
	+	\|-
	+	\| ...0001'''0000'''
	+	\| 1.0
	+	\|-
	+	\| ...0001'''0001'''
	+	\| 1.0625
	+	\|}
	+
	+	The Scanse Sweep lidar unit is connected to an Arduino Micro to capture and process range, angle, and signal quality data during a scan.
	+
	+
	+
	+

← Older revision	Revision as of 19:24, 6 June 2019
(No difference)