- The motor mounted feedback is blind to torsion of the shaft with load.
- The coupler between the motor and the lead screw distorts under load, causing error between the motor shaft and the lead screw.
- The lead screw itself can also exhibit torsion under load, varying with both load and position of the nut with respect to the driven end of the screw.
- The lead screw itself typically has periodic error which can be very expensive to minimize, and the nut backlash minimization can add load as well as wear to the system.
- Finally, the thrust bearings' accuracy also directly affects the system.

- Dual loop control can improve the performance of a motion control system.
- System cost and complexity required for the desired level of precision can be reduced.
- A 100-fold increase in mechanical stiffness of the motion system was achieved with a secondary feedback device integrated in the motor.

- Machine retrofits with lean automation add higher product quality; decrease wiring and programming time.
- OPA Consulting Services adds modular manufacturing and higher controls performance to high-end fabric production.
- The Quantum Group achieves 10%-15% improvements in woven product quality with 50% less I/O wiring time and 30% less programming time.

- Verifying that pipes and connectors can withstand the forces applied to them in subsea drilling environments requires extremely rigorous testing.
- Conventional testing equipment has limited capabilities when it comes to applying force, which sometimes prevents equipment manufacturers from testing products to their maximum limits.
- Test system can produce millions of pounds of axial and bending force on an assembled pipe stand, comparable to the harshest subsea drilling conditions.

In the formula, is the difference of two carrier phase integer ambiguities of antenna M and antenna N between two epochs; is the difference of two phase fractions of antenna M and antenna N between two epochs; is the difference of two actual distances from antenna M and N to the same satellite between two epochs. Then the equation (3) is linearized. By assuming that the approximation of the baseline vector MN is , its correction is , approximation of carrier phase integer ambiguity is , and its correction is δN_MN^jk, we can get the following error equation: In the formula, If there are n satellites, antenna M and N observed at time t, we could get n-1 error equations. At the same time, we need n-1 carrier phase integer ambiguities. So there are (n-1)+3 unknown numbers. By observing p epochs with antenna M and N, we can get p(n-1) error equations. Thus we get redundant observations that could be solved with least the squares principle [11]. The error equation can be put into matrix form: V=AX+W (5) In this formula, A is the coefficient matrix. By assuming that each double-differenced measurement value is equal and independent of each other, we can get the equation: NX + D = 0 (6) In the formula,

The accuracy of point O coordinates can be tested by comparing for equivalence the two distance values. L

- From the moment installation is complete at 10:39 to 11:15, the portal crane is in a stationary state. Compared with the latter dynamic observation data, the baseline length, pitch angle, and direction angle are most stable in this period.
- From the moment the portal crane begins work at 11:17 to 11:30, it only has swing action with minimum radius (22 meters) at 60 degrees and maximum radius (45 meters) at 30 degrees, and the direction angle remains unchanged at 80 degrees.
- From 11:30 to 12:50, the portal crane rotates with the load in maximum radius. The change trend of direction angle shows that the portal crane rotates horizontally two round-trips at constant speed during this period. Because the swing arm elevation angle is the minimum, the locus of the direction angle may have a slight jitter, which will stay at 0 degrees (360 degrees) finally.
- From 12:50 to 15:19, the direction angle remains the same except from 13:04 to 13:24, when the portal crane stops running. All portal cranes do luffing lifting work, so the baseline length and direction angle are stable.
- From 15:19 to 16:02, the portal crane does variable rotation until it stops working and its swing arm parallels to the orbit; namely, it points to the landside.

- Real-time altitude monitoring of portal cranes can be performed using global navigation satellite system (GNSS) and real-time kinematic (RTK) measurements.
- Measurements can be used to help with crane monitoring in real time, calculating position, velocity of points, and baseline attitude information at the same time.
- Products can be customized based on the monitoring functions required.

Choosing the right metrics isn’t always a cut and dried matter. As we look at RCM metrics, I am going to add another dimension to the metrics decision—that of process.

Manufacturing processes are different—while automobiles and gasoline both are produced in manufacturing processes and both generally considered highly dependent on the other for their usefulness, the way you make them could not be more different.

In addition to the vast differences in the equipment used in manufacturing in both plants, robots versus huge distillation columns, the typical refinery operates 24 hours a day every day of the year, while an automobile plant typically runs one or two shifts a day and five days a week. In this case, both the physical process variations as well as the production process variations lead to very different maintenance needs.

In a continuous process like refining, uptime is a holy grail. If you go down for any reason, production comes to a halt and that time is non-recoverable. In situations like this, the emphasis on asset performance is centered on detecting imminent failure and preventing it.

In failure modes and effects analysis (FMEA), you analyze how equipment might fail, what effect that failure might have, and then what steps you can take to prevent that failure from occurring. In this type of production environment, your RCM focus needs to be aligned to the uptime goal and the elements which the various FMEA activities identify as the most critical to achieving that objective.

In a discrete manufacturing process like in an automotive or aerospace plant, there may be significant periods of time available for maintenance activity. By extending operational capacity for a few hours or days, activities might differ considerably.

In many discrete manufacturing operations there are parallel work centers, such as a robot painting operations, where downtime in a single cell only slows but does not stop operation. In this case, there are numerous opportunities to recover the lost production through overtime or process reconfiguration. In this environment, KPIs or metrics that measure flexibility and contribute to machine center OEE and maintenance cost-effectiveness might be more relevant than in the continuous-process plant example.
-*Edited by Bob Vavra, Content Manager, Plant Engineering, bvavra@cfemedia.com *

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