How exactly segway works

The Segway personal transporter is a device that transports one person at relatively low speeds. The low-speed (limited to approximately 20 kmph) operation combined with its electric propulsion system makes the Segway a candidate for providing short-distance transportation on city streets, sidewalks, and inside buildings. When a Segway is in use, the device is driven by two wheels that are placed side-by-side, rather than the standard in-line configuration of a bicycle or a motorcycle. When the operator leans forward, the wheels turn in unison in the same direction to provide forward motion. In order to stop, the wheels must accelerate forward to get out in front of the system's centre of mass and then apply a deceleration torque to slow the system down without causing the operator to fall forward off the device. These operating principles are reversed to allow the system to move backward.

            In order to turn, the wheels rotate at unequal speeds causing the system to travel in an arc. If the system is not translating forward or backward, then the wheels can rotate in opposite directions to turn the machine in place.However,it is not possible for the human operator to balance the device, as they can with a human-powered inverted pendulum such as a unicycle. The sensors in the device must constantly be measuring the state of the machine and feeding this information to the computer controller. The controller then uses this feedback signal to adjust the wheel speed so that the forward/backward (pitch) falling motion is maintained within an acceptable envelope so that device and rider do not fall over. Note that under many operating conditions, the system is mechanically stable in the side-to-side (roll) direction. Therefore, the computer does not attempt to control the roll motion. Assuming wheel-ground rolling stiction, the system is also stable in the yaw direction.However, the computer must change the yaw rate in order to turn the machine in 10 response to the operator input. It also limits the turning rate to a maximum value.

Fig1 Segway

  A Segway is often used to transport a user across mid range distances in urban environments. It has more degrees of freedom than car/bike and is faster than pedestrian. However a navigation system designed for it has not been researched. The existing navigation systems are adapted for car drivers or pedestrians. Using such systems on the Segway can increase the driver's cognitive workload and generate safety risks.

Physics Behind Segway

The physics behind segway:

The Segway is a uniquely sophisticated machine that uses on-board computers working with multiple sensors and redundant physical systems to sense the motions of the rider, and to react to those motions. The “Stand up Scooter” requires the rider to learn how the machine will respond to the throttle and brake, while physically holding on to the machine to counter the unbalanced forces of acceleration and deceleration.

Fig1 Forces acting on segway rider

Diagram A, on the left shows person standing, with gravity and the Segway reaction force in balance. In diagram B Person has leaned forward to start moving. The purple arrow is gravity/weight.The magenta arrow is the reaction force of person against the Segway. The dashed blue line is the vector sum of the two. If the Segway doesn’t respond person will fall forward as the Segway is pushed backward. Diagram C shows the response of the Segway as it senses the tilt of the Segway platform as person leans forward. The computers order the motors to power the wheels and accelerate the Segway. The force of acceleration is the red arrow, and the reaction force of the Segway to person is the orange arrow. The dashed yellow line is the vector sum of the two. Diagram D shows that the sum of the forces in diagrams B and C are in balance. The vector sums run through each other and the rider, so there are no unbalanced forces or torque. The on-board computers adjust the power to the wheels to keep the forces balanced through the rider. This is what makes the Segway unique.

Fig 2: Segway Balances the Forces on the Rider in All Phases of Riding

Fig 2 shows how the Segway keeps the rider in balance during all phases of a ride: stationary, accelerating, cruising at 6 mph, and decelerating. This continuous balancing of forces is what makes riding the Segway possible. There are no unbalanced forces to topple the rider off the Segway, which is why many people with diseases or injuries which result in muscular weakness, such as Muscular Dystrophy or Multiple Sclerosis, can safely ride a Segway. They do not have to compensate for unbalanced forces with their own strength - the Segway does it for them.

On a Segway you initiate moving forward by leaning forward. The Segway senses your leaning and accelerates forward, balancing the forces, and you are underway. This is the process shown in Fig 2 above. The beauty of this is that the Segway is controlled by same set of reflexes and reactions that control basic human locomotion. Even if you can’t walk due to physical limitations, you retain these reflexes and reactions.

Components Required To Make a Cheap Segway

The approximated cost in INR is Rs 24,000

Environmental Benefits from Segway

•The Segway  has many benefits for you and the environment.

•It will reduce the impact of global warming by checking greenhouse gas output and fossil fuel consumption.

•If we are able to replace 10% of 900 million car travel to 3 mile with the Segway  there would be:  

§6.2 million fewer gallons of gas consumed.

§286 million fewer pounds of CO2 emitted every day.

How segway works?? ..(Part1)

How Segway Works??

Concept Behind Segway

The Segway is a dynamic system that is commonly referred to as an inverted pendulum. The Segway and rider form a more complicated inverted pendulum that has uncertain time-varying dynamics. Non-inverted pendulums, like crane payloads and the oscillating arm inside a grandfather clock, swing back and forth in a stable manner with limited amplitude. These types of dynamic systems occur throughout the world in useful products. On the other hand, inverted pendulums do not naturally swing back and forth with a well-controlled oscillation. Rather, they fall over. The simplest form of an inverted pendulum consists of a mass attached through a massless rod to a base mass. This is commonly known as a cart-pendulum system.

INVERTED PENDULUM

  

    

      The cart is free to move horizontally. The rod is connected to the cart through a rotational pin joint. This system is in unstable equilibrium when the rod is standing upright. Mathematically, this equilibrium can be maintained as long as there are no input forces whatsoever on the system. However, such conditions do not exist in real systems and some means of stabilization is needed to maintain the pendulum in the upright position. A force F must be applied to the cart in order to move the cart pivot back and forth from one side of the pendulum mass centre to the other side. The pendulum is always falling over, but the cart motion tries to keep the leaning angle at a small level.

       When a Segway is in use, the device is driven by two wheels that are placed side-by-side, rather than the standard in-line configuration of a bicycle or a motorcycle. When the operator leans forward, the wheels turn in unison in the same direction to provide forward motion. In order to stop, the wheels must accelerate forward to get out in front of the system's centre of mass and then apply a deceleration torque to slow the system down without causing the operator to fall forward o_ the device. These operating principles are reversed to allow the system to move backward. In order to turn, the wheels rotate at unequal speeds causing the system to travel in an arc.

       If the system is not translating forward or backward, then the wheels can rotate in opposite directions to turn the machine in place. Given the side-by-side wheel configuration, and the elevated centre of mass, the mechanical design of the transporter is unstable. It will fall over if the computerized control system is not continuously turning the wheels. This constant adjusting of the device is similar to a person balancing an inverted broom in their hand. In order to keep the broom upright, the person must continually move their hand in the direction that the broom is falling. The hand must pass to the other side of the broom's centre of mass to generate a torque that will cause the broom to start rotating in the opposite direction. As a result, the broom is always falling, but the hand motion keeps changing the direction of the fall.

       Just like the inverted broom, the Segway and rider are always falling. However, it is not possible for the human operator to balance the device, as they can with a human-powered inverted pendulum such as a unicycle. The sensors in the device must constantly be measuring the state of the machine and feeding this information to the computer controller. The controller then uses this feedback signal to adjust the wheel speed so that the forward/backward (pitch) falling motion is maintained within an acceptable envelope so that device and rider do not fall over. Note that under many operating conditions, the system is mechanically stable in the side-to-side (roll) direction. Therefore, the computer does not attempt to control the roll motion. Assuming wheel-ground rolling friction, the system is also stable in the yaw direction. However, the computer must change the yaw rate in order to turn the machine in response to the operator input.

Abstract for Segway

This project involves in designing a machine using electronic system to make an inverted pendulum remain upright. Inverted pendulum is our system which will be used in a machine and that machine is known as Segway. The pendulum will hang freely on an axle so that it can swing clockwise and counterclockwise. The axle in turn will be able to move along a straight line along the direction in which the pendulum swings. By dynamically driving a motor which moves the axle along a track according to the motion of the segway, the segway will be prevented from falling from the upright position.

The problem of controlling an inverted pendulum in this manner is classical to control systems, since the system is inherently unstable – the segway will not remain upright without external forces. This type of system is also very difficult to control manually, and therefore requires the use of electronic controls.

In this project, a control algorithm will be developed and implemented digitally, using a microprocessor and sensors, and a working demonstration will be built. Ultimately, this project will show the effectiveness of a digital control system to stabilize a machine quickly, and it will be used for transportation purposes. 

Research That Has Been Already Done On Segway

•Dean Kamen is the inventor of Segway.

•Major research done on segway are related to its performance.

•Segway are available in various models such as Basic model i.e. Segway i2 while there is also another model i.e. Segway x2 which is used for adventurous rides.

•Automatic obstacle avoidance in Segway.

•Smart battery usage and more intelligent models are being made.

Why Segway ?

When I first saw Segway on television it was really fascinating for me and I wanted to take a ride on this particular machine. So I've decided to build this machine on my own in my last year of  Mechanical Engineering. Hence I decided to make a cheap segway as my final year Engineering Project.

Few Problem Statements due to which I enthusiastically accepted this challenge were as follows:

•There is no personal transporter in India other than bike , cars etc.

•People use bike for traveling short distances which give rise to consumption of fossil fuels as well as pollution.

•In India the most basic personal transporter medium is bike which costs around more than 45-50 thousands.

•For few physically challenged people they only rely on wheel chairs. So even for them a personal carrier system is absent in India.

•In official Segway Dean Kamen has used 10 microprocessors while in our Segway we are going to use single microprocessor with additional electronic components which will decline rate.

•Power supply is from Li-ion battery which is costly we are going to use Lead Acid battery which is quite cheap.

•Material used in branded segway is a composite material which is again quite costly and hard to manufacture