TechArchive

Original article date: May 2000

Most brakes simply operate as ‘on/off’ devices, but this often proves to be unsatisfactory. Tommy Miller describes a new intelligent brake from Lenze.

Although conventional spring-operated brakes perform adequately when they are simply required to prevent motion, there is often a need to slow a machine progressively or to use the brake to help control the motion. To solve this problem, traditionally users have been required to use complex multi-stage brakes and associated switching logic.

A new development, however, allows standard spring-operated brakes to be controlled in such a way that the braking torque applied is within the range 20 to 100% of the brake’s rated torque. By taking advantage of the system’s Canbus communications link, the torque applied by the brake can be controlled concurrently with the torque applied by a drive, allowing enhanced motion control to be achieved.

Automatic monitoring

A further advantage of the new system is that brake wear can be monitored automatically, even to the extent that alarms can be raised if the wear reaches a predefined level, or if the number of applications of the brake exceeds a certain amount or the operating time becomes excessive. This all contributes to improved reliability and reduced maintenance – and hence lower operational costs.

Introduced to the UK by Lenze, the system is being described as a mechatronic braking system with Moditorque control. The company’s standard BFK-series spring-operated brakes are suitable for use with the control system, with the brakes’ rated torques ranging from 8 to 400Nm. The Moditorque control system is available in three operating voltages: 24V, 48V and mains voltages. Programming is achieved by means of a Windows-based software package.

Almost any type of automation or special-purpose machinery could benefit from the additional control, depending on the process and whether the equipment or material being processed might suffer from being over-braked. However, Lenze also highlights that fork-lift trucks are an area where the signal from a foot pedal could easily be translated into a progressive braking action on the wheels – with synchronisation between multiple brakes being easily achieved via the Canbus communications.

Escalator drives and cranes both have to carry variable loads, so these two types of equipment could also be improved by the addition of more braking control and the facility for remotely monitoring the level of wear. In addition, cranes could make good use of the synchronisation between the torque supplied by the drive and the torque applied by the brake.

Whatever the application, the Moditorque system seems to bring spring-operated braking a long way forward from the traditional all-or-nothing approach.

• Lenze

May 2000