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Speed Wobble
Speed wobble (also known as shimmy, tank-slapper, or death wobble) is a rapid side-to-side shaking of a vehicle's wheel(s) that occurs at high speeds and can lead to loss of control. It presents as a quick (4–10 Hz) oscillation of primarily the steerable wheel(s), and is caused by a combination of factors, including initial disturbances and insufficient damping, which can create a resonance effect. Initially, the rest of the vehicle remains mostly unaffected, until translated into a vehicle yaw oscillation of increasing amplitude, producing loss of control. Vehicles that can experience this oscillation include motorcycles and bicycles, skateboards, and, in theory, any vehicle with a single steering pivot point and a sufficient amount of freedom of the steered wheel, including that which exists on some light aircraft with tricycle gear where instability can occur at speeds of less than ; this does not include most automobiles. The initial instability occurs mostly at h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Damping
In physical systems, damping is the loss of energy of an oscillating system by dissipation. Damping is an influence within or upon an oscillatory system that has the effect of reducing or preventing its oscillation. Examples of damping include viscous damping in a fluid (see viscous drag), surface friction, radiation, resistance in electronic oscillators, and absorption and scattering of light in optical oscillators. Damping not based on energy loss can be important in other oscillating systems such as those that occur in biological systems and bikes (ex. Suspension (mechanics)). Damping is not to be confused with friction, which is a type of dissipative force acting on a system. Friction can cause or be a factor of damping. Many systems exhibit oscillatory behavior when they are disturbed from their position of static equilibrium. A mass suspended from a spring, for example, might, if pulled and released, bounce up and down. On each bounce, the system tends to return to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hopf Bifurcation
In the mathematics of dynamical systems and differential equations, a Hopf bifurcation is said to occur when varying a parameter of the system causes the set of solutions (trajectories) to change from being attracted to (or repelled by) a fixed point, and instead become attracted to (or repelled by) an oscillatory, periodic solution. The Hopf bifurcation is a two-dimensional analog of the pitchfork bifurcation. Many different kinds of systems exhibit Hopf bifurcations, from radio oscillators to railroad bogies. Trailers towed behind automobiles become infamously unstable if loaded incorrectly, or if designed with the wrong geometry. This offers a gut-sense intuitive example of a Hopf bifurcation in the ordinary world, where stable motion becomes unstable and oscillatory as a parameter is varied. The general theory of how the solution sets of dynamical systems change in response to changes of parameters is called bifurcation theory; the term ''bifurcation'' arises, as the set ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self-oscillation
Self-oscillation is the generation and maintenance of a periodic motion by a source of power that lacks any corresponding periodicity. The oscillator itself controls the phase with which the external power acts on it. Self-oscillators are therefore distinct from forced and parametric resonators, in which the power that sustains the motion must be modulated externally. In linear systems, self-oscillation appears as an instability associated with a negative damping term, which causes small perturbations to grow exponentially in amplitude. This negative damping is due to a positive feedback between the oscillation and the modulation of the external source of power. The amplitude and waveform of steady self-oscillations are determined by the nonlinear characteristics of the system. Self-oscillations are important in physics, engineering, biology, and economics. History of the subject The study of self-oscillators dates back to the early 1830s, with the work of Robert Wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pilot-induced Oscillation
Pilot-induced oscillations (PIOs), as defined by MIL-HDBK-1797A, are ''sustained or uncontrollable oscillations resulting from efforts of the pilot to control the aircraft''. They occur when the aviator, pilot of an aircraft inadvertently commands an often increasing series of corrections in opposite directions, each an attempt to cover the aircraft's reaction to the previous input with an overcorrection in the opposite direction. An aircraft in such a condition can appear to be "porpoising" switching between upward and downward directions. As such it is a coupling of the frequency of the pilot's inputs and the aircraft's own frequency. In order to avoid any assumption that oscillation is necessarily the fault of the pilot, new terms have been suggested to replace ''pilot-induced oscillation''. These include ''aircraft-pilot coupling'', ''pilot–in-the-loop oscillations'' and ''pilot-assisted (or augmented) oscillations''. The physics of flight make such oscillations more probab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hunting Oscillation
Hunting oscillation is a self-oscillation, usually unwanted, about an Mechanical equilibrium, equilibrium. The expression came into use in the 19th century and describes how a system "hunts" for equilibrium. The expression is used to describe phenomena in such diverse fields as electronics, aviation, biology, and railway engineering. Railway wheelsets A classical hunting oscillation is a swaying motion of a railway vehicle (often called ''truck hunting'' or ''bogie hunting'') caused by the Adhesion railway#Directional stability and hunting instability, coning action on which the directional Directional stability, stability of an adhesion railway depends. It arises from the interaction of adhesion forces and inertial forces. At low speed, adhesion dominates but, as the speed increases, the adhesion forces and inertial forces become comparable in magnitude and the oscillation begins at a critical speed. Above this speed, the motion can be violent, damaging track and wheels and pote ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fishtailing
Fishtailing is a vehicle handling problem which occurs when the rear wheels lose traction, resulting in oversteer. This can be caused by low-friction surfaces (sand, gravel, rain, snow, ice, etc.). Rear-wheel drive, Rear-drive vehicles with sufficient power can induce this loss of traction on any surface, which is called Understeer and oversteer, power-oversteer. Mechanics and causes Accidental fishtailing During fishtailing, the rear end of the car skids to one side, which must be offset by the driver counter-steering, which is turning the front wheels in the same direction as the skid, (e.g. left if the rear swings left) and reducing engine power. Over-correction will result in a skid in the opposite direction; hence the name. Without a proper driver's reaction, the fishtailing vehicle will spin completely. Friction is the main reason this action is effective. If a car is moving across a surface in any direction other than the direction it is pointed, it is Skid (automobi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caster Flutter
A caster (or castor) is an undriven wheel that is designed to be attached to the bottom of a larger object (the "vehicle") to enable that object to be moved. Casters are used in numerous applications, including shopping carts, office chairs, toy wagons, hospital beds, and material handling equipment. High capacity, heavy duty casters are used in many industrial applications, such as platform trucks, carts, assemblies, and tow lines in plants. Types Casters may be fixed to roll along a straight line path, or mounted on a pivot or pintle such that the wheel will automatically align itself to the direction of travel. Rigid casters A basic, rigid caster consists of a wheel mounted to a stationary fork. The orientation of the fork, which is fixed relative to the vehicle, is determined when the caster is mounted to the vehicle. An example of this is the wheels found at the rear of a shopping cart in North America. Rigid casters tend to restrict vehicle motion so that the vehicle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bicycle And Motorcycle Dynamics
Bicycle and motorcycle dynamics is the science of the motion of bicycles and motorcycles and their components, due to the forces acting on them. Dynamics falls under a branch of physics known as classical mechanics. Bike motions of interest include balancing, steering, braking, accelerating, suspension activation, and vibration. The study of these motions began in the late 19th century and continues today. Bicycles and motorcycles are both single-track vehicles and so their motions have many fundamental attributes in common and are fundamentally different from and more difficult to study than other wheeled vehicles such as dicycles, tricycles, and quadracycles. As with unicycles, bikes lack lateral stability when stationary, and under most circumstances can only remain upright when moving forward. Experimentation and mathematical analysis have shown that a bike stays upright when it is steered to keep its center of mass over its wheels. This steering is usually supplied b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Onewheel
Onewheel is a self-balancing electric skateboard with a single tire, used as a means of transportation and for boardsports. Riders place their feet on either side of the tire to face sideways, leaning forward to accelerate and leaning backward to slow down. The board was engineered to emulate the feeling of snowboarding on powder. Launched in 2014 by Kyle Doerksen, the project raised over $630,000 on Kickstarter. Since then, 9 Onewheel models have been introduced, with the latest being released in November 2024. The Onewheel lineup includes the Pint, Pint X, Pint S, XR Classic, GT, and the GT S-Series, which has a top speed of 25 mph and a range up to 25 miles. Discontinued models include the original Onewheel, Onewheel+, and Onewheel+ XR. They have been ridden in 139 countries, covering over 170 million miles (273 million kilometers) with more than 300,000 riders globally. History Future Motion Inc. founder and CEO Kyle Doerksen created a commercial version of the Onewheel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Unicycle
An electric unicycle (often initialized as EUC or acronymized yuke or Uni) is a self-balancing personal transporter with a single wheel. The rider controls speed by leaning forwards or backwards, and steers by twisting or tilting the unit side to side. The self-balancing mechanism uses accelerometers and gyroscopes. Most manufacturers of EUCs are based out of China, including Segway, Inmotion, Kingsong, Begode, and Leaperkim. Operation Similar to hoverboards, Onewheels, and Segways, electric unicycles are self-balancing in a forward and backward direction, with side-to-side (lateral) stability being provided by human steering motions that tilt or twist the unit, similar to Bicycle and motorcycle dynamics. The control of a unicycle can be considered to be similar to an inverted pendulum. Many electric unicycles have suspension, either operated by air or springs. Electric unicycles come in varying speeds, battery capacities, and motor wattages. Low-end models may have speeds up ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornering Force
Cornering force or side force is the lateral (i.e., parallel to wheel axis) force produced by a vehicle tire during cornering. Cornering force is generated by tire slip and is proportional to slip angle at low slip angles. The rate at which cornering force builds up is described by relaxation length. Slip angle describes the deformation of the tire contact patch, and this deflection of the contact patch deforms the tire in a fashion akin to a spring. As with deformation of a spring, deformation of the tire contact patch generates a reaction force in the tire; the cornering force. Integrating the force generated by every tread element along the contact patch length gives the total cornering force. Although the term, "tread element" is used, the compliance in the tire that leads to this effect is actually a combination of sidewall deflection and deflection of the rubber within the contact patch. The exact ratio of sidewall compliance to tread compliance is a factor in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bicycle Suspension
A bicycle, also called a pedal cycle, bike, push-bike or cycle, is a human-powered or motor-assisted, pedal-driven, single-track vehicle, with two wheels attached to a frame, one behind the other. A is called a cyclist, or bicyclist. Bicycles were introduced in the 19th century in Europe. By the early 21st century there were more than 1 billion bicycles. There are many more bicycles than cars. Bicycles are the principal means of transport in many regions. They also provide a popular form of recreation, and have been adapted for use as children's toys. Bicycles are used for fitness, military and police applications, courier services, bicycle racing, and artistic cycling. The basic shape and configuration of a typical upright or "safety" bicycle, has changed little since the first chain-driven model was developed around 1885. However, many details have been improved, especially since the advent of modern materials and computer-aided design. These have allow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
