Gravitational and friction terms play an important role in achieving high performance control of heavy-duty hydraulic machines, such as excavators. In this paper, a new approach for decoupled estimation of the gravitational parameters is presented. Static experiments are carried out with an instrumented computer-controlled mini excavator to estimate the gravitational parameters. Load pins are u...

A sphere moving down the surface of a static sphere and a simple phase diagram. Abstract A small sphere placed on the top of a big static fric-tionless sphere, slips until it leaves the surface at an angle θ l = cos −1 2/3. On the other extreme, if the surface of the big sphere has coefficient of static friction , µ s → ∞, the small sphere starts rolling and continues to do so until it leaves t...

A friction identification method in a frequency domain is proposed for a precision servomechanism. A nonlinear friction model including static, Coulomb, and viscous friction as well as Stribeck effect is considered in this paper. Friction models are formulated by using describing functions. Friction elements are estimated through the limit cycle analysis in a velocity control loop. A Butterwort...

A sphere moving down the surface of a static sphere and a simple phase diagram. Abstract A small sphere placed on the top of a big static fric-tionless sphere, slips until it leaves the surface at an angle θ l = cos −1 2/3. On the other extreme, if the surface of the big sphere has coefficient of static friction , µ s → ∞, the small sphere starts rolling and continues to do so until it leaves t...

A new dynamic friction force model for the longitudinal road/tire interaction for wheeled ground vehicles is validated via experiments with an actual passenger vehicle. Contrary to common static friction/slip maps, this new dynamic friction model is able to accurately capture the transient behavior of the friction force observed during transitions between braking and acceleration. A velocitydep...

a new dynamic friction model for modeling of elliptical vibration assisted turning (evat) was developed in this research. the periodic change of the friction force direction is known to be one of the most important causes of this phenomenon. in modeling of machining processes (including the evat process), static coulomb friction model was employed by most of the researchers. because of the peri...

This paper reviews rock friction and the frictional properties of earthquake faults. The basis for rateand state-dependent friction laws is reviewed. The friction state variable is discussed, including its interpretation as a measure of average asperity contact time and porosity within granular fault gouge. Data are summarized showing that friction evolves even during truly stationary contact, ...

A new procedure for deriving nonlinear mathematical modeling for a specific class of aerospace hydro - mechanical control valves is presented. The effects of friction on the dynamic behavior of these types of valves along with the experimental verifictions are also given. The modeling approach is based on the combination of the following three tasks: decomposition of the valve into simple speci...