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Abstract: This paper describes a sliding mode observer scheme for estimation of the shear force affecting the cantilever in a Transverse Dynamic Force Microscope (TDFM). The vertically oriented cantilever is oscillated in the proximity to the specimen under investigation. The amplitude of oscillation of the cantilever tip is affected by these shear forces. They are created by the ordered‐water layer above the specimen. The oscillation amplitude is therefore a measure of distance between the tip and the surface of the specimen. Consequently, the estimation of the shear forces provides useful information about the specimen characteristics. For estimating the shear forces, an approximate finite dimensional model of the cantilever is created using the method of lines. This model is subsequently reduced in terms of its order. An unknown input sliding mode observer has been used to reconstruct the unknown shear forces using only tip position measurements and the cantilever excitation. This paper describes the development of the sliding mode scheme and presents experimental results from the TDFM set up at the Centre for Nanoscience and Quantum Information (NSQI) at Bristol University. [ABSTRACT FROM AUTHOR]

In this paper, the problem of estimating the shear force affecting the tip of the cantilever in a Transverse Dynamic Force Microscope (TDFM) using a real-time implementable sliding mode observer is addressed. The behaviour of a vertically oriented oscillated cantilever, in close proximity to a specimen surface, facilitates the imaging of the specimen at nano-metre scale. Distance changes between the cantilever tip and the specimen can be inferred from the oscillation amplitudes, but also from the shear force acting at the tip. Thus, the problem of accurately estimating the shear force is of significance when specimen images and mechanical properties need to be obtained at submolecular precision. A low order dynamic model of the cantilever is derived using the method of lines, for the purpose of estimating the shear force. Based on this model, an estimator using sliding mode techniques is presented to reconstruct the unknown shear force, from only tip position measurements and knowledge of the excitation signal applied to the top of the cantilever. Comparisons to methods assuming a quasi-static harmonic balance are made. [ABSTRACT FROM AUTHOR]

This article presents a novel linear actuated chain test rig, which is capable of accelerated test speeds and continuous wear measurements. The ability to measure chain wear in situ saves time and expense compared to a conventional sprocket driven rig because the traditional rig requires the chain to be dismantled in order to monitor wear. In situ chain measurement reduces errors significantly. The novel test rig does not have a traditional set up of rotary driven sprocket and chain but uses a pneumatic linear actuator to articulate a short section of chain, which is preloaded between two cantilevers. This design leads to a compact rig with only few moving parts and allows accelerated testing at high frequencies. Linear encoder displacement transducers are used to measure changes in chain length down to 0.06 µm at a rate of 4000 readings per second. Sample wear tests on different chains have been conducted to compare life test results with conventional sprocket-driven tests rig. A good correlation was obtained between the steady-state wear rate for three different brands of roller chain. [ABSTRACT FROM PUBLISHER]