Let’s hit the road

When is one architectural approach used over another? There is no easy, simple answer, and sometimes two architectures can be used with success for a given application.

In broad terms, the more cost sensitive the application, the more likely it is that you will design your own card, and if possible, integrate on-board amplifiers. Since you are designing your own card you can choose exactly the connectors you want, and dimension the form factor of the card for your own application. Highly synchronized applications such as machine tools will gravitate toward either a multi-axis motion card, or more likely a tightly-coupled distributed drive approach. While not cheap, these drives allow a lot of flexibility in motor type and power range. Don’t forget that you will still need a motion control card for overall path generation, and to correctly split up and send out the motion segments to each individual drive axis. Be aware that in theory the card and the drive could be from separate vendors, but in practice this is seldom the case.

The larger middle ground of applications such as medical automation, semiconductor automation, scientific instrumentation, and low-power general automation, is generally served by loosely- coupled distributed drives, or by multi-axis motion cards. Factors that tilt the solution toward distributed drives include larger number of axes, and use of two or more different motor types. Factors which tilt the solution toward multi-axis cards are the need for synchronization, smaller number of axes, or use of a single motor type.

Another factor in determining the importance of adopting drives versus a multi-axis motion card architecture is the physical size of the machine. Generally speaking, the larger the system, the greater the reliability improvement in locating the drive close to the motor. But if the whole machine is already fairly small, locating the drive close to the motor will not be a big factor in the decision.