F13: Obstacle Avoidance Robot - Revision history

Preet at 02:28, 9 December 2013

2013-12-09T02:28:27Z

Preet: /* Grading Criteria */

2013-12-09T02:25:23Z

‎Grading Criteria

Proj user8: /* Software Design */

2013-12-07T22:15:15Z

‎Software Design

Proj user8 at 18:20, 7 December 2013

2013-12-07T18:20:22Z

Proj user8: /* Conclusion */

2013-12-07T04:19:32Z

‎Conclusion

Proj user8: /* Software Design */

2013-12-07T04:13:49Z

‎Software Design

Proj user8: /* Implementation */

2013-12-07T03:59:30Z

‎Implementation

Proj user8: /* Implementation */

2013-12-07T03:45:46Z

‎Implementation

Proj user8: /* Implementation */

2013-12-07T03:18:45Z

‎Implementation

Proj user8: /* Hardware Interface */

2013-12-07T02:46:39Z

‎Hardware Interface

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 == Objectives & Introduction ==
 === Team Members & Responsibilities ===
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 == Schedule ==
 {| class="wikitable"
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 == Design & Implementation ==
 The photo below shows the implementation/progress as of 11/10/2013.
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 === Hardware Design ===
 The design is built onto a Pololu 5" round robotic chassis that is designed to accept two independently driven wheels.  As Figure 1 shows, there are two electronic boards stacked onto each other.  The board on top is the SJSU NXP LPC1758 development board.  Below that is a board that contains the motor driver and the 12V to 5V regulator.  This board also worked well for a power distribution board so several headers are located on this board.
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 === Hardware Interface ===
 The design uses the SJSU board PWM and GPIO outputs to drive the scan head servo motors and wheel motors.  The GPIO are also utilized for the inputs from the digital sensors.  An A/D input into the board reads voltage from the analog I/R sensor.
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 === Software Design ===
 We have working functions that can drive the motors forwards and backwards and turn the robot left and right.  Other functions read the A/D input from the analog I/R sensor.  The status of the digital I/R connected to the GPIO are also read.  The main functionality of the algorithm is to drive forward until an object is sensed.  If one of the digital I/R sensors sensed the object, then the robot backs up for more clearance.  The scan head is then used to find the clearest path and the wheels turn the robot in that direction and begin moving forward again.
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 === Implementation ===
 ====Infrared (I/R) Sensors====
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 == Testing & Technical Challenges ==
 === Issue #1 ===
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 == Conclusion ==
 The Obstacle Avoidance Robot utilized nearly as many hardware skills as it did software skills.  There were many challenges in trying to connect the various pieces of hardware with all of their unique requirement ranges.  Everything from different voltage requirements to varying frequency requirements.  There were also software limitations to overcome as well.  For instance, it would have been nice to be able to have two different PWM frequencies at the same time: one for the motors and another for the servos.  However we found that we were able to make enough compromises to get the hardware and software to work well enough together without needlessly overcomplicating the design.
 === Project Videos ===
 The video below shows the first autonomous testing of the motor functionality.
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 === Project Source Code ===
 == References ==
 === Acknowledgement ===
 === References Used ===
 === Appendix ===

← Older revision		Revision as of 02:25, 9 December 2013
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−	~~=== Grading Criteria ===~~
−	~~<font color="green">~~
−	* How well is Software & Hardware Design described?
−	* How well can this report be used to reproduce this project?
−	* Code Quality
−	* Overall Report Quality:
−	** Software Block Diagrams
−	** Hardware Block Diagrams
−	**: Schematic Quality
−	** Quality of technical challenges and solutions adopted.
−	~~</font>~~
−
	= Object Sensing and Avoidance Robot =		= Object Sensing and Avoidance Robot =

← Older revision		Revision as of 22:15, 7 December 2013
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	Two different implementations of the algorithm were tried. One with interrupts and one without interrupts (polling). Without some sort of masking functionality, interrupts do not work well. This is discussed further in the "Issues" section.		Two different implementations of the algorithm were tried. One with interrupts and one without interrupts (polling). Without some sort of masking functionality, interrupts do not work well. This is discussed further in the "Issues" section.
		+
		+	Below are brief descriptions of each of the software functions.
		+
		+	====Main Function====
		+
		+	The main function declares all the variables and initializing functions. It scans the switch (sw1) on the board, to enable the robot. When a button press is detected, the main obstacle avoidance function is called.
		+
		+	====check_ir_sensor_function====
		+
		+	This function is the main algorithm for this robot. The function works by first adjusting the threshold of the analog Infra-Red sensor as function of the external light.
		+
		+	It will then scan the digital IR sensors and the analog IR sensor. If an object was detected on the digital sensor, the robot will reverse a few inches and call the “distance_scan_function”.
		+
		+	If an object was detected on the analog sensor and the reading is below the set threshold, it will call the “distance_scan_function”.
		+
		+	When computing the “distance_scan_function”, the results of the scan are sent to the motors object to turn the robot into the clearest path. Once pointed to the clearest path, it will then continue strait.
		+
		+	====distance_scan_function====
		+
		+	This function is the “head scanning” function. It scans 5 angles of view in front of the robot, reading the A/D on each angle and storing the read into an array. When all 5 measurements are complete, it will find the farthest distance and store into the return value.
		+
		+	When using the interrupt version, everything remains the same, except the digital sensors are not being polled, rather firing an interrupt when detecting an object. The interrupts need to be enabled in the main function. The interrupts will then call the ir_irq function.
		+
		+	====ir_irq====
		+
		+	This function will turn on an LED to indicate the interrupt. The function will then stop the motors immediately, reverse the robot a few inches and will then call the "distance_scan_function".

	====Algorithm with Interrupts====		====Algorithm with Interrupts====

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 ====Algorithm with Interrupts====
 ====Algorithm without Interrupts (Polling)====
 === Implementation ===
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 ====Infrared (I/R) Sensors====
-Two types of I/R sensors were used.  The first was an analog sensor shown in Figure 6 below.  The analog sensor can gauge the approximate distances to objects based on the calibration found above.  The sensor sits on the scanning head of the robot and is used to find the clearest path for the robot to go next.
+Two types of I/R sensors were used.  The first was an analog sensor shown in Figure 9 below.  The analog sensor can gauge the approximate distances to objects based on the calibration found above.  The sensor sits on the scanning head of the robot and is used to find the clearest path for the robot to go next.
-[[File:obstacle_analogir_det.png|thumb|upright=1.5|none|Figure 6: Analog I/R Sensor Detail]]
+[[File:obstacle_analogir_det.png|thumb|upright=1.5|none|Figure 9: Analog I/R Sensor Detail]]
-Figure 7 below shows the detailed location of the digital sensors.  These sensors change state when an object is approximately 2 - 10cm in front of them.  The main purpose of the digital sensors is to provide more coverage area for sensing objects.  While the robot is moving forward, the digital sensors are used to find objects lower and to the side compared to what the main scanning head can see.
+Figure 10 below shows the detailed location of the digital sensors.  These sensors change state when an object is approximately 2 - 10cm in front of them.  The main purpose of the digital sensors is to provide more coverage area for sensing objects.  While the robot is moving forward, the digital sensors are used to find objects lower and to the side compared to what the main scanning head can see.
-[[File:obstacle_digitalir_det.png|thumb|upright=1.5|none|Figure 7: Digital I/R Sensor Detail]]
+[[File:obstacle_digitalir_det.png|thumb|upright=1.5|none|Figure 10: Digital I/R Sensor Detail]]
 ====Wheels and Motors====
-Two independently controlled wheels were used.  A motor controller was considered in the beginning, but ultimately a motor driver was utilized instead.  A motor controller usually contains all of the functions to drive the motors and is typically commanded via I2C or similar communication bus.  A motor driver, on the other hand, basically amplifies a PWM signal that is sent to it and will also contain direction controls.  For this robot, a motor driver was used since the NXP microcontroller already contained PWM and motor controller functionality.  It was thought that this solution would provide the most versatility.  Figure 8 below shows the motor and motor driver being tested on a bread board before being implemented onto the robot platform.
+Two independently controlled wheels were used.  A motor controller was considered in the beginning, but ultimately a motor driver was utilized instead.  A motor controller usually contains all of the functions to drive the motors and is typically commanded via I2C or similar communication bus.  A motor driver, on the other hand, basically amplifies a PWM signal that is sent to it and will also contain direction controls.  For this robot, a motor driver was used since the NXP microcontroller already contained PWM and motor controller functionality.  It was thought that this solution would provide the most versatility.  Figure 11 below shows the motor and motor driver being tested on a bread board before being implemented onto the robot platform.
-[[File:obstacle_testmotor.png|thumb|upright=1.5|none|Figure 8: Motor Breadboard]]
+[[File:obstacle_testmotor.png|thumb|upright=1.5|none|Figure 11: Motor Breadboard]]
 As mentioned above, the PWM functionality of the microcontroller was used to run the motors through the motor drivers.  In software, different functions were created for going forward, backwards, turning right and turning left.  The different functions are needed to set the "A" and "B" GPIO correctly as these lines control whether and individual motor will turn forward or backward.  For example to make a right hand turn, the left wheel should move forward while right wheel turns backwards.

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 == Conclusion ==
 ''Conclude your project here.  You can recap your testing and problems.  You should address the "so what" part here to indicate what you ultimately learnt from this project.  How has this project increased your knowledge?''
 === Project Videos ===

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 ''Show your software design.  For example, if you are designing an MP3 Player, show the tasks that you are using, and what they are doing at a high level.  Do not show the details of the code.  For example, do not show exact code, but you may show psuedocode and fragments of code.  Keep in mind that you are showing DESIGN of your software, not the inner workings of it.''
-We have working functions that can drive the motors forwards and backwards and read from the I/R sensor.  The plan is to find a generally clear direction to go from the I/R sensor input.  This function will send a direction to go to the motor drive section.  Currently, we are investigating the use of interrupts in order to tie all of the pieces together to make it function smoothly.
+We have working functions that can drive the motors forwards and backwards and turn the robot left and right.  Other functions read the A/D input from the analog I/R sensor.  The status of the digital I/R connected to the GPIO are also read.  The main functionality of the algorithm is to drive forward until an object is sensed.  If one of the digital I/R sensors sensed the object, then the robot backs up for more clearance.  The scan head is then used to find the clearest path and the wheels turn the robot in that direction and begin moving forward again.
 === Implementation ===

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 The chart below shows the calibration data from each of the four sensors on the I/R sensor head.
-[[File:obstacle_Cal_data.jpg|Frame|none|Figure 6: I/R Sensor Calibration]]
+[[File:obstacle_Cal_data.jpg|frame|none|Figure 6: I/R Sensor Calibration]]
 From this data, we were able to determine that a sensor reading less than 1000 counts meant that an object was far enough away to take no action. However a reading of greater than 1000 counts meant that an object is getting closer than 5 to 6 inches and it is time to stop the robot from going forward and run an algorithm to determine the best direction to move the robot.