Motion control technology from ERIKS has been incorporated into a new physical therapy device for treating back pain. This is precisely programmed to provide the correct seating position and resistance, resulting in the patient needing fewer treatments and recovering more quickly

Working alongside physical movement expert Danielle Engels, engineering company Onder de Linden has developed Mobex, a physical therapy device for treating back pain.

Existing machinery for the treatment of back pain relies on gravitational forces to provide resistance and only a standard seat which allows for free movement. These work solely based on the principles used in gymnasium fitness equipment, in which the user forces a set of weights upward that are counterbalanced by gravitational force. With this concept, however, only a limited number of back muscles are exercised and other muscles in the body have to be involved.

The objective was therefore to devise a system that would enable more accurate control of the treatment of nonspecific lower back pain using resistors instead of weights.

The design

The new physical therapy device, which helps patients to recover from back pain by performing physical exercises on an apparatus that is
precisely programmed to provide the correct seating position and resistance via actuators and controls, features motion control solutions from ERIKS.
The design for Mobex was put into action after the concept was entered into a design challenge competition at Power Transmissions Fair in Utrecht during 2010, which is open to projects in the field of motion control. The prize was 40 engineering hours, in which time the system was successfully developed.


The Mobex comprises five linear actuators with amplifiers, a servo motor amplifier, an in-house printed circuit board and a PC with dedicated software running under Windows XP.  All components of the motion control system communicate by means of a CANopen fieldbus system. The five linear actuators allow adjustment of the seat, footrests and knee clamps, while the control software stores patient settings so that the therapist can reset the equipment for each individual patient at the push of a button. 

Before treatment, a physiotherapist manually loosens tensed muscles, allowing the patient to move more easily. The patient is then seated in the Mobex, which is carefully adjusted to set his or her body into a precise position then programmed to demand a precise level of exercise from the patient’s back muscles. The motion control system enables the physiotherapist to vary the load depending on the patient’s condition and the type of exercise required.

Back treatment using the Mobex has proved to be extremely successful. Fewer treatments are said to be needed compared to conventional methods of therapy, which means faster recovery for patients as well as reduced costs of care. 

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