Harmonic drive

Stroke-adjustable quasi-harmonic drive single and multi-cylinder... 

Figure 12. The dependence of the activation energy R on the amplitude A of the harmonic driving force F(t) =A cos (1.2r) as determined [141] by electronic experiment (filled circles), numerical sumulations (open circles) and analytical calculation (solid line), based on (28) for an overdamped duffing oscillator U q) = —q2/2 +

The control rod drive (CRD) mechanisms are located in the upper part of the ONCA as shown in Figure 4.3-1. A single mechanism is illustrated in Figure 4.3-7. It consists of a dc torque motor, harmonic drive unit which provides an 80 1 speed reduction, and the cable storage drum. The control rod is lowered and raised with a flexible aircraft quality steel cable which is taken up on the cable storage drum. Small cable guide rollers locate the cable in the proper position above the gamma shield penetration. 

Control rod position indication is accomplished with redundant precision potentiometers. The multiturn movement of the cable drum shaft is reduced with small harmonic drive speed reducers to less than one revolution on the potentiometer shaft. 

All bearings in the CRD are precision ball bearings which are lubricated with a special grease that has been developed for this type of low radiation and moderate temperature application. This lubricant, which is also used in the harmonic drive components, has been subjected to long duration tests in helium. Therefore, the possibility of bearing or speed reducer seizure from deterioration of the lubricant is minimized. Relubrication of these components at regular maintenance intervals is planned. 

Due to the very low harmonic level inherent to the ISU converter, the drives based on this technology are referred to as Low Harmonic Drives. (See Figure 6.)... 

Note that the actuator s rotors also contribute to the apparent mass of the robot. To estimate their contribution, the same reasoning can be applied, with all equations expressed, however, at the motor level. It can be proven that the apparent inertia of the actuators increases as a fimction of R. As a consequence, the inertia of systems using large reducers, for example, harmonic drives, is relatively important (often larger than the links apparent inertia) and requires force-sensing and force-control closed loops to reduce it. On the contrary, the inertia of actuation units using low-reduction-ratio cable capstan reducers is usually very limited (much smaller than the link s inertia). 

Constant Velocity versus Harmonic Drive Friction Measurements... 

The harmonic drive approach which is basic in rheological experiments was first implemented by Colchero et al. (25) for an AFM. The basic idea couples a lock-in technique with the lateral force microscope and has been essentially used for measuring the lateral contact stiffness (26,27). If the tip is modulated periodically in successive back and forth scans the lateral force signal is periodic too. The lock-in technique is particularly appropriate to analyze a signal in reference to another signal of the same frequency. 

A harmonic drive voltage has been applied to the transverse piezo transducer. We increased the amplitude of the sine wave drive at a constant frequency, which led to a progressive increase in the the sliding velocity defined in rheological conditions by v=Ax CO. Figure 5 presents the lateral force, the friction coefficient and the loss tangent, as a function of the sliding velocity of the cantilever, v=Ax (O. 

The phase response function can therefore also be measured using this harmonic drive method. It can similarly be obtained using a shaking table. 

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