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The printed circuit boards (PCB) that I use are made from FR-4. FR-4 is fiberglass sheets glued together with a epoxy resin. Circuit boards made from FR-4 are rigid and very strong. The rigidity and strength of the PCB make it suitable to replace the aluminum and acrylic decking in my previous mobile robots. Since FR-4 has suitable strength and rigidity for the chassis, and I can use it for PCBs, it makes sense to combine the needed electronics onto the chassis. The energy source, voltage regulation, connectors, computing, and sensing will be built on the base deck. The base deck will also support the propulsion motors, the rear castor, and will include mounting holes for additional decks.
Making the robot’s decking out of the PCB will combine the electronics and the chassis structure, and also reduce the overall cost. One draw back to this concept is that there will be exposed circuitry that can be susceptible to damaging Electro-Static Discharge (ESD). I have a preliminary solution to this problem that I'll work out and write about in a later blog. Until then...
- keep rockin
Making the robot’s decking out of the PCB will combine the electronics and the chassis structure, and also reduce the overall cost. One draw back to this concept is that there will be exposed circuitry that can be susceptible to damaging Electro-Static Discharge (ESD). I have a preliminary solution to this problem that I'll work out and write about in a later blog. Until then...
- keep rockin
Mobile Autonomous Robotic Concept
Within the last few years, there has been substantial growth of robotics in academia and in the hobby world. That makes it an exciting time to be in the robotics field. Researchers are using mobile robots to find solutions to carry out dangerous and dirty jobs. Jobs like the exploration of caves in a combat environment, waste clean up, and disaster relief. They are also exploring and fielding the use of autonomous robots for automobile driving, oceanographic exploration, agriculture, facility security, and piloting aircraft.
As the need to field autonomous robots grows, so does the need to educate and train future robotics engineers. Greater numbers of college students are introduced to robotics every year. Many colleges offer graduate degrees focusing on robotics and intelligent system development. Some are even offering undergraduate degrees in robotics. Students enrolled in electrical engineering and computer science undergraduate programs are using mobile robots to complete design projects. All of this use and growth of robotics has fueled a real need for mobile robots.
While each roboticists has a unique problem to solve and each ground mobile robot has a unique set of requirements, there is often a set of characteristics that many robots share. Those are...
*An on-board energy source
*A method of propelling itself
*Voltage regulation
*A microcontroller or microprocessor
*Connectors to link devices to the micro
*A set of useful sensors and actuators
As the requirements for the project and robot change over time one doesn't want to have to change the hardware. It would be better to build into the robot a certain amount of flexibility to add sensors, actuators, and additional processing power. Therefore it is desirable to build a robot that allows for changes and additions. It is also strongly desirable for the mobile robot to be easy to use with ubiquitous serial interfaces for micro code uploads and debugging. A widely available energy source such as AA or AAA batteries is also desirable to reduce the situation where one finds themselves unable power up the robot because they can't re-energize their batteries or buy fresh ones!
The focus on this development project is the creation of a autonomous mobile robot that has applications in research, education, and in the hobby world. Can a mobile robot be developed that is feature rich, includes interfaces for customization, be reliable, affordable, and easy to use?
-keep rockin
We All Need Support
There will be plenty of challenges in the design of a useful and affordable mobile robot. The number of challenges can be kept down by keeping the design as simple as possible. The design should be kept as simple as possible to eliminate unnecessary complications and challenges. The simplicity of the design will be governed by the requirements and features outlined in the last blog. The principle of keeping the design simple will be applied to all aspects of the robot, including the chassis.
I'm making a mobile robot intended to move on the floor or ground. It could do this by walking or rolling along. One leg of a walking robot will require at least two servo motors. A walking robot will require at least four legs. This puts the minimum servo count at eight. That's eight servos to mount and control. A gait algorithm would be needed, and it won't go very fast. If it rolls, it would need two wheels and one motor per wheel for a total of two motors. No gait algorithm would be needed either. Right off the bat, the rolling robot seams much easier to implement.
DC electric motors are commonly used to drive wheels on a robot. And of the various wheel configurations, the differential steer locomotion is the most common because of the simplicity of controlling motors for both speed and direction. Differential steer of two wheels can require as little as only two control signals. I want the robot to have the ability to drive up and down ramps. This requirement rules out one differential configuration where the two drive wheels are placed in the mid-line of the robot, and the front and back of the robot each mounts a castor. As the robot drives up the ramp the castor makes contact with the ramp first and the drive wheels loose contact with the floor
Less is more. If we eliminate the front castor and move the drive wheels near the front of the robot, we get a simple footprint and the ability to ascend and descend ramps. I’ve used this wheel and castor arrangement on a couple of other robots, and it has performed very well on carpet and hard surface flooring. Robots also perform well when making the transition to and from both. This footprint also makes it possible to drive over low profile obstacles like pencils, magazines, and electrical cords.
-keep rockin
Two Birds, One Stone
Establishing the locomotion method and footprint was the fist step in my chassis design. Every mobile robot requires a few essential systems; they are, power, computing, sensing and locomotion. The robot will need at lease one circuit board for voltage regulation, computing, connectors and sensors. In past designs I used aluminum and plastic sheets to build decks of the chassis. The propulsion motors attached to the base deck and additional decks stacked up to mount circuit cards, sensors and actuators. For the most part, the decks did nothing more than to serve as a place to attach these devices.
Within the last few years, there has been substantial growth of robotics in academia and in the hobby world. That makes it an exciting time to be in the robotics field. Researchers are using mobile robots to find solutions to carry out dangerous and dirty jobs. Jobs like the exploration of caves in a combat environment, waste clean up, and disaster relief. They are also exploring and fielding the use of autonomous robots for automobile driving, oceanographic exploration, agriculture, facility security, and piloting aircraft.
As the need to field autonomous robots grows, so does the need to educate and train future robotics engineers. Greater numbers of college students are introduced to robotics every year. Many colleges offer graduate degrees focusing on robotics and intelligent system development. Some are even offering undergraduate degrees in robotics. Students enrolled in electrical engineering and computer science undergraduate programs are using mobile robots to complete design projects. All of this use and growth of robotics has fueled a real need for mobile robots.
While each roboticists has a unique problem to solve and each ground mobile robot has a unique set of requirements, there is often a set of characteristics that many robots share. Those are...
*An on-board energy source
*A method of propelling itself
*Voltage regulation
*A microcontroller or microprocessor
*Connectors to link devices to the micro
*A set of useful sensors and actuators
As the requirements for the project and robot change over time one doesn't want to have to change the hardware. It would be better to build into the robot a certain amount of flexibility to add sensors, actuators, and additional processing power. Therefore it is desirable to build a robot that allows for changes and additions. It is also strongly desirable for the mobile robot to be easy to use with ubiquitous serial interfaces for micro code uploads and debugging. A widely available energy source such as AA or AAA batteries is also desirable to reduce the situation where one finds themselves unable power up the robot because they can't re-energize their batteries or buy fresh ones!
The focus on this development project is the creation of a autonomous mobile robot that has applications in research, education, and in the hobby world. Can a mobile robot be developed that is feature rich, includes interfaces for customization, be reliable, affordable, and easy to use?
-keep rockin
We All Need Support
There will be plenty of challenges in the design of a useful and affordable mobile robot. The number of challenges can be kept down by keeping the design as simple as possible. The design should be kept as simple as possible to eliminate unnecessary complications and challenges. The simplicity of the design will be governed by the requirements and features outlined in the last blog. The principle of keeping the design simple will be applied to all aspects of the robot, including the chassis.
I'm making a mobile robot intended to move on the floor or ground. It could do this by walking or rolling along. One leg of a walking robot will require at least two servo motors. A walking robot will require at least four legs. This puts the minimum servo count at eight. That's eight servos to mount and control. A gait algorithm would be needed, and it won't go very fast. If it rolls, it would need two wheels and one motor per wheel for a total of two motors. No gait algorithm would be needed either. Right off the bat, the rolling robot seams much easier to implement.
DC electric motors are commonly used to drive wheels on a robot. And of the various wheel configurations, the differential steer locomotion is the most common because of the simplicity of controlling motors for both speed and direction. Differential steer of two wheels can require as little as only two control signals. I want the robot to have the ability to drive up and down ramps. This requirement rules out one differential configuration where the two drive wheels are placed in the mid-line of the robot, and the front and back of the robot each mounts a castor. As the robot drives up the ramp the castor makes contact with the ramp first and the drive wheels loose contact with the floor
Less is more. If we eliminate the front castor and move the drive wheels near the front of the robot, we get a simple footprint and the ability to ascend and descend ramps. I’ve used this wheel and castor arrangement on a couple of other robots, and it has performed very well on carpet and hard surface flooring. Robots also perform well when making the transition to and from both. This footprint also makes it possible to drive over low profile obstacles like pencils, magazines, and electrical cords.
-keep rockin
Two Birds, One Stone
Establishing the locomotion method and footprint was the fist step in my chassis design. Every mobile robot requires a few essential systems; they are, power, computing, sensing and locomotion. The robot will need at lease one circuit board for voltage regulation, computing, connectors and sensors. In past designs I used aluminum and plastic sheets to build decks of the chassis. The propulsion motors attached to the base deck and additional decks stacked up to mount circuit cards, sensors and actuators. For the most part, the decks did nothing more than to serve as a place to attach these devices.