*   Instrumented walkers and canes

 

Applications

Instrumented ambulatory aides provide the means to study upper body kinesiology during assisted gait.  During use, the forces and moments applied to the hand grips of the ambulatory aid are measured with a multiaxis load cell built into the structure of the aid device.  Knowledge of these forces and moments can lead to a better understanding of the assisted ambulatory process and can result in improved individual rehabilitation and understanding of assisted ambulatory function.

Available devices

AMTI offers several off the shelf designs which integrate AMTI’s high accuracy MCW series multiaxis transducers with different manufacturer’s ambulatory assistance products.  Several different adult and pediatric ambulatory assistance devices are listed in the table below.

 

  

AMTI
Model No.

Walker/device
manufacturer

Description

Model no.

AAW

Guardian

Adult anterior non-folding “V” brace walker

7720

PAW

Guardian

Pediatric anterior bail fold “A” frame walker

7749

PPW2

Kaye

Pediatric posterior walker (small)

WB2

PPW3

Kaye

Pediatric posterior walker with wheels

W3B

ACR

Guardian

Adult forearm crutches

5161

PCR

Guardian

Pediatric forearm crutches

5162

ACN

Guardian

Adult offset handle cane

5355

PCN

Guardian

Pediatric offset handle cane

5357

 

Retrofit devices

AMTI has instrumented a large variety of walkers, canes and crutches to meet the needs of our customers.  Please contact us if you would like a quotation to retrofit AMTI’s MCW series multiaxis transducer to a particular ambulatory aid that you supply.  Contact us for:

*       Retrofit canes

*       Retrofit crutches

*       Retrofit walkers

Instrument operation

The MCW series walker sensors are multiaxis sensors that measure the three orthogonal applied forces (Fx, Fy and Fz) and the three orthogonal applied moments (Mx, My and Mz).  Walker designs usually incorporate two sensors, one for each of the walker handles.  The MCW sensors are mounted such that all of the load applied to the handles of the walker are transmitted through the sensors into the body of the walker and thus ultimately to the ground.  This arrangement allows you to isolate and examine the forces that are acting on the walker and/or on the ambulatory subject.  The vertical force represents the amount of weight bearing that is transmitted through the walker, the anterior/posterior force represents the upper body’s contribution to acceleration or deceleration of movement, whereas the forces to the left and right represent stabilizing forces or are the result of motion artifacts. 

Signal conditioning

 The MCW walker sensors are strain gage type sensors. As with all conventional strain gage transducers, bridge excitation and signal amplification are required.  AMTI’s MiniAmp or DigiAmp can be used to provide the required six channels of amplification and excitation required by each sensor. These amplifiers process the sensor’s low-level signals and provide outputs suitable for an A/D converter so that the data can be stored and processed by a computer. 


Transducer specifications

The MCW walker sensors are available in three different capacities, 250, 500 and 1000 pounds.  Note that the rated capacity is specified by the Fz channel capacity.  The Fx and Fy channel capacities are approximately one-half of the Fz capacity.  Typically the lower capacities will be used for pediatric applications whereas the higher capacities will be suitable for adult applications.

MCW SERIES SPECIFICATIONS

Rated Fz Capacity

250

500

1000

Fx, Fy Capacity,
lb, (N)

125
(550)

250
(1100)

500
(2200)

Fz Capacity
lb, (N)

250
(1100)

500
(2200)

1000
(4400)

Mx, My Capacity
in*lb, (Nm)

250
(28)

500
(56)

1000
(112)

Mz Capacity
in*lb, (Nm)

125
(14)

250
(28)

500
(56)

Fx, Fy Sensitivity
µV/[V*lb], (µV/[V*N])

12.0
(2.7)

6.0
(1.35)

3.0
(0.65)

Fz Sensitivity
µV/[V*lb], (µV/[V*N])

3.0
(0.65)

1.5
(0.34)

0.75
(0.17)

Mx, My Sensitivity
µV/[V*in*lb], (µV/[V*Nm])

30
(265)

15
(132)

7.5
(66)

Mz Sensitivity
µV/[V*in*lb], (µV/[V*Nm])

24
(212.4)

12
(97.4)

6.0
(50.4)

Fx, Fy Stiffness
X105 lb/in, (X107 N/m)

0.12
(0.2)

0.3
(0.5)

0.6
(1.0)

Fz Stiffness
X105 lb/in, (X107 N/m)

1.7
(3)

4.5
(8)

9.0
(16)

Mz Stiffness
X104 in*lb/radian, (X104 Nm/radian)

2.0
(0.2)

5.0
(0.5)

10
(1.1)

 

Note 1:  The specifications listed above are for estimating purposes. Actual precision calibrations are furnished with each instrument.

 

 

Advanced Mechanical Technology, Inc.

 

Phone: 1-617-926-6700