Height of goods . . . Stair climbing . . . Prototyping blues . . .
Dear Search Engineer: I need to determine the height of goods being transported on sliding tables that are stored one on top of the other, so I can determine how close the tables can be. One possibility would be to use several photoeyes, but the height resolution will be dependent on the number of sensors used. Any other methods I should consider? —F.C. in NJ
Dear F.C.: Here's a couple solutions. First, consider ultrasonic sensors, which operate as sonar systems. They transmit an ultrasonic signal and determine distance by measuring the time that the ultrasonic signal takes to make a round trip from the sensor's emitter to an object or surface and back to the sensor's receiver. A single transducer on the sensor may function as both the emitter and the receiver, thus making the sensor assembly more compact. These sensors have good range and resolution. Depending on sensor positioning and aiming in your application, a single sensor may be all that is needed. Another suggestion: If you have ample height above the conveyor, install a dangling arm and an angle sensor at its pivot near the ceiling; that will give you the height data you seek. If you don't have the room between pallets for the swinging arm to come down, another way is to put a drop arm above the pallets at one point, and when the load comes, just let it drop; when halted by the load, retract automatically.
Most Honorable Search Engineer: I've been looking for a design for trolleys that can climb stairs with a payload ranging from 200-400 kg. These are intended to carry industrial gas cylinders. —S.Y., Malaysia
Dear S.Y.: Consider a cog railway, a chain or belt or cable railway, or spoked wheels where the spokes are cams.
G'Day Search Engineer: I'm a final year mechatronic engineering student. I'm hoping to simulate and model the output (movement) of a Terfenol-D rod that I plan on using on a micropump system. I hope to model it by a neural network using MATLAB and Simulink. —I.A., Australia
Hey Mate: I think you may be falling into the typical trap of so many young students and new engineers, namely substituting excessive computer modeling for common sense and some initial rough prototyping to get a hands-on feel for the scope of the problem. Many new engineers can waste time blindly simulating basically simple, straightforward engineering problems in excruciating detail; then they are shocked when they discover that the real device behaves differently. Try to step away from you computer and work at getting an intuitive understanding of this problem first.
Dear Search Engineer: I'd like to know what type of sensor I could use to measure the reaction force on a timing-belt tensioner, taking into account conditions such as oil, heat, water, etc. —K.G. in CA
Dear K.G.: I suggest you incorporate a strain gauge into the tensioner arm or element. This would give you a continuous dynamic force indication. You can then calibrate statistically.