Patent ID: 8828095

Claim:
Passive orthopedic aid being a foot prosthesis or foot orthosis, comprising a first part and a second part both rotatably connected to each other by a swivel joint, so as to allow a rotation movement between the first part and the second part having a certain movement resistance, a sensor arrangement for measuring parameters that provide indications of instantaneous operation requirements of the orthopedic aid, a control means connected to the sensor arrangement including a processor arrangement configured to determine operation requirements and to generate control signals corresponding to the determined operation requirements, a controllable hydraulic damping arrangement configured to modify the movement resistance of the rotation movement between the first part and the second part and being controlled by the control signals of said control means, wherein the control of the orthopedic aid is passive, the damping arrangement is a hydraulic cylinder with two hydraulic chambers separated from each other by a piston, the hydraulic chambers are connected via two connection lines permitting a flow of hydraulic fluid between the hydraulic chambers in one flow direction only where the flow directions in the two connection lines are opposite to each other, flow resistances in the two connection lines are controlled by the control arrangement separately, each connection line having an own adjustment means for adjusting different flow resistances during a gait cycle, the processor arrangement includes an ankle moment sensor configured to detect where an ankle moment crosses zero during said gait cycle, the processor arrangement is configured to determine a current neutral point position for each gait cycle from a zero crossing of the ankle moment detected by the ankle moment sensor, and the control means is configured to take into account the current neutral point position determined by the processor arrangement from the zero crossing of the ankle moment for generating the control signals which control the flow resistances in the two connection lines.