Mechanical Components
Common mechanical components in a mechatronic system may be classified into some useful groups, as follows:
1. Load bearing/structural components (strength and surface properties)
2. Fasteners (strength)
3. Dynamic isolation components (transmissibility)
4. Transmission components (motion conversion)
5. Mechanical actuators (generated force/torque)
6. Mechanical controllers (controlled energy dissipation)
In each category we have indicated within parentheses the main property or attribute that is characteristic of the
function of that category.
In load bearing or structural components the main function is to provide structural support. In this context, mechanical strength and surface properties (e.g., hardness, wear resistance, friction) of the component are crucial. The component may be rigid or flexible and stationary or moving. Examples of load bearing and structural components include bearings, springs, shafts, beams, columns, flanges, and similar load-bearing structures.
Fasteners are closely related to load bearing/structural components. The purpose of a fastener is to join two mechanical components.
Here as well, the primary property of importance is the mechanical strength. Examples are bolts and nuts, locks and keys, screws, rivets, and spring retainers. Welding, bracing, and soldering are processes of fastening and will fall into the same category.
Dynamic-isolation components perform the main task of isolating a system from another system (or environment) with respect to motion and forces.
These involve the “filtering” of motions and forces/torques.
Hence motion transmissibility and force transmissibility are the key considerations in these components. Springs, dampers, and inertia elements may form the isolation element.
Shock and vibration mounts for machinery, inertia blocks, and the suspension systems of vehicles are examples of isolation dynamic components.
Transmission components may be related to isolation components in principle, but their functions are rather different. The main purpose of a transmission component is the conversion of motion (in magnitude and from). In the process the force/torque of the input member is also converted in magnitude and form.
In fact in some applications the modification of the force/torque may be the primary requirement of the transmission component. Examples of transmission components are gears, harmonic drives, lead screws and nuts (or power screws), racks and pinions, cams and followers, chains and sprockets, belts.
Mechanical actuators are used to generate forces (and torques) for various applications. The common actuators are electromagnetic in form (i.e., electric motors) and not purely mechanical.
Since the magnetic forces are “mechanical” forces which generate mechanical torques, electric motors may be considered as electromechanical devices. Other types of actuators that use fluids for generating the required effort may be considered in the category of mechanical actuators.
Examples are hydraulic pistons and cylinders (rams), hydraulic motors, their pneumatic counterparts, and thermal power units (prime movers) such as steam/gas turbines. Of particular interest in mechatronic systems are the electromechanical actuators and hydraulic and pneumatic actuators.
Mechanical controllers perform the task of modifying dynamic response (motion and force/torque) in a desired manner. Purely mechanical controllers carry out this task by controlled dissipation of energy. These are not as common as electrical/electronic controllers and hydraulic/pneumatic controllers. In fact hydraulic/pneumatic servo valves may be treated in the category of purely mechanical controllers.
Furthermore, mechanical controllers are closely related to transmission components and mechanical actuators. Examples of mechanical controllers are clutches and brakes.
In selecting a mechanical component for a mechatronic application, many engineering aspects have to be considered. The foremost are the capability and performance of the component with respect to the design requirements (or specifications) of the system.
For example, motion and torque specifications, flexibility and deflection limits, strength characteristics including stress-strain behavior, failure modes and limits and fatigue life, surface and material properties (e.g., friction, nonmagnetic, noncorrosive), operating range, and design life will be important. Other factors such as size, shape, cost, and commercial availability can be quite crucial.
Rather, we select for further analysis a few important mechanical components that are particularly useful in mechatronic systems.
