Design of the HLPR Chair 

Design of the HLPR Chair 

Home Lift Position and Rehabilitation Chair 

Roger Bostelman 

James Albus 

Intelligent Systems Division 

Manufacturing Engineering Laboratory 

National Institute of Standards and Technology 

June 19, 2007 

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Table Contents 

Introduction......................................................................................................................... 3 

Wheelchairs..................................................................................................................... 3 

Patient Lift ...................................................................................................................... 3 

Introduction References.................................................................................................. 4 

Concept ............................................................................................................................... 6 

Prototype............................................................................................................................. 9 

Specifications.................................................................................................................... 12 

Mechanical Design............................................................................................................ 13 

HLPR Chair Component Labels................................................................................... 17 

Modifications to Original Designs.................................................................................... 51 

Electrical Design............................................................................................................... 70 

Towards Autonomous Control.......................................................................................... 81 

Stability Testing................................................................................................................ 87 

Prototype Cost Estimate.................................................................................................... 88 

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Introduction 

Reference [1] says “today, approximately 10 percent of the world’s population is over 

60; by 2050 this proportion will have more than doubled” and “the greatest rate of 

increase is amongst the oldest old, people aged 85 and older.” She follows by adding that 

this group is subject to both physical and cognitive impairments more than younger 

people. These facts have a profound impact on how the world will maintain the elderly 

independent as long as possible from caregivers. Both physical and cognitive 

diminishing abilities address the body and the mental process of knowing, including 

aspects such as awareness, perception, reasoning, intuition and judgment. Assistive 

technology for the mobility impaired includes the wheelchair, lift aids and other devices, 

all of which have been around for decades. However, the patient typically or eventually 

requires assistance to use the device; whether it’s someone to push them in a wheelchair, 

to lift them from the bed to a chair or to the toilet or for guiding them through cluttered 

areas. With fewer caregivers and more elderly, there is a need for improving these 

devices to provide them independent assistance. 

Wheelchairs 

There has been an increasing need for wheelchairs over time. L.H.V. van der Woude 

[2] states that mobility is fundamental to health, social integration and individual wellbeing of the humans. Henceforth, mobility must be viewed as being essential to the 

outcome of the rehabilitation process of wheelchair dependent persons and to their 

successful (re-)integration into society and to a productive and active life. Thrun [3] said 

that, if possible, rehabilitation to relieve the dependence on the wheelchair is ideal for this 

type of patient to live a longer, healthier life. Van der Woude continues stating that many 

lower limb disabled subjects depend upon a wheelchair for their mobility. Estimated 

numbers for Europe and USA are respectively 2.5 million and 1.25 million. The quality 

of the wheelchair, the individual work capacity, the functionality of the wheelchair/user 

combination, and the effectiveness of the rehabilitation program do indeed determine the 

freedom of mobility. 

Patient Lift 

Just as important as wheelchairs are the lift devices and people who lift patients into 

wheelchairs and other seats, beds, automobiles, etc. The need for patient lift devices will 

also increase as generations get older. When considering if there is a need for patient lift 

devices, several references state the positive, for example: 

• “The question is, what does it cost not to buy this equipment? A back injury can cost 

as much as $50,000, and that’s not even including all the indirect costs. If a nursing 

home can buy these lifting devices for $1,000 to $2,000, and eliminate a back injury 

that costs tens of thousands of dollars, that’s a good deal,” [4] 

• 1 in every 3 nurses become injured from the physical exertion put forth while moving 

non-ambulatory patients; costing their employers $35,000 per injured nurse. [5] 

• 1 in 2 non-ambulatory patients fall to the floor and become injured when being 

transferred from a bed to a wheelchair. - [6] 

• "Nursing and personal care facilities are a growing industry where hazards are known 

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and effective controls are available," said OSHA Administrator John Henshaw. "The 

industry also ranks among the highest in terms of injuries and illnesses, with rates 

about 2 1⁄2 times that of all other general industries..." [7] 

• “Already today there are over 400,000 unfilled nursing positions causing healthcare 

providers across the country to close wings or risk negative outcomes. Over the 

coming years, the declining ratio of working age adults to elderly will further 

exacerbate the shortage. In 1950 there were 8 adults available to support each elder 

65+, today the ratio is 5:1 and by 2020 the ratio will drop to 3 working age adults per 

elder person.” [8] 

In 2005, NIST ISD began the Healthcare Mobility Project to target this staggering 

healthcare issue of patient lift and mobility. ISD researchers looked at currently available 

technology through a survey of patient lift and mobility devices [9]. That report showed 

that there is need for technology that includes mobility devices that can lift and maneuver 

patients to other seats and technology that can provide for rehabilitation to help the 

patient become independent of the wheelchair. 

An additional area investigated in the survey was intelligent wheelchairs. NIST has 

been studying intelligent mobility for the military, transportation, and the manufacturing 

industry for nearly 30 years through the Intelligent Control of Mobility Systems (ICMS) 

Program. [10] Toward a standard control system architecture and advanced 3D imaging 

technologies, as being researched within the ICMS Program, and applying them to 

intelligent wheelchairs, NIST has begun outfitting the HLPR Chair with computer 

controls. Although throughout the world there are or have been many research efforts in 

intelligent wheelchairs, including: [11, 12, 13, 14] and many others, the authors could 

find no sources applying standard control methods nor application of the most advanced 

3D imagers prototyped today to intelligent wheelchairs. Therefore, NIST began 

developing the HLPR Chair [15] to investigate these specific areas of mobility, lift and 

rehabilitation, as well as advanced autonomous control. 

This paper includes mechanical and electrical designs for the HLPR Chair in its 

prototype stage with designs dating back to December 2005. An initial prototype HLPR 

Chair concept, called RoboChair, was completed in July 2004. 

Introduction References 

[1] Pollack, Martha, “Intelligent Technology for Adaptive Aging” Presentation, AAAI-04 

American Association for Artificial Intelligence Conference Keynote Address, 2004 

[2] L.H.V. van der Woude , M.T.E. Hopman and C.H. van Kemenade, “Biomedical 

Aspects of Manual Wheelchair Propulsion: The State of the Art II,” Volume 5, Assistive 

Technology Research Series, 1999, 392 pp., hardcover 

[3] Thrun, Sebastian, Visit to Stanford University to discuss healthcare mobility devices, 

August 2006. 

[4] Marras, William, “Lifting Patients Poses High Risk for Back Injuries,” Ohio State 

University, http://researchnews.osu.edu/archive/resthome.htm. 1999. 

[5] Blevins, Healthcare Statistics: Blevins Medical, Inc., 

http://www.patientlift.net/282164.html. 2006 

[6]U.S. Bureau of Labor Statistics, from Blevins website: 

http://www.patientlift.net/282164.html, 1994. 

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[7] John Henshaw, http://www.osha.gov/SLTC/ nursinghome/solutions.html, 

Occupational Safety and Health Administration, 2005 

[8] Wasatch Digital iQ, “InTouch Health's Remote Presence Robot Used by Healthcare 

Experts,” http://www.wasatchdigitaliq.com/parser.php?nav=article&article_id=43, Santa 

Barbara, CA & Salt Lake City --(Business Wire)--June 16, 2003. 

[9] Bostelman, Roger; Albus, James, “Survey of Patient Mobility and Lift Technologies 

Toward Advancements and Standards” NISTIR #7384, 2006. 

[10] NIST Intelligent Control of Mobility Systems Program website: 

http://www.isd.mel.nist.gov/ research_areas/mobility/index.htm 

[11] Kuno, Y., Murashima, T., Shimada, N., Shirai, Y., "Intelligent Wheelchair Remotely 

Controlled by Interactive Gestures," International Conference on Pattern Recognition, 

vol. 04, no. 4, p. 4672, 2000. 

[12] Patel, S., Jung, S-H., Ostrowski, J., Rao, R., Taylor, C., “Sensor based door 

navigation for a nonholonomic vehicle,” GRASP Laboratory, University of Pennsylvania, 

Proceedings of the 2002 IEEE International Conference on Robotics and Automation, 

Washington, DC, May 2002. 

[13] Song W.-K.; Lee H.; Bien Z., “KAIST - KARES: Intelligent wheelchair-mounted 

robotic arm system using vision and force sensor,” Robotics and Autonomous Systems, 

vol. 28, no. 1, pp. 83-94(12), 31, Publisher: Elsevier Science, July 1999. 

[14] Yanco, H., Hazel, A., Peacock, A., Smith, S. and Wintermute, H. “Initial Report on 

Wheelesley: A Robotic Wheelchair System,” Department of Computer Science, 

Wellesley College, 1995 

[15] Bostelman, R., Albus, J., “HLPR Chair – A Service Robot for the Healthcare 

Industry,” 3rd International Workshop on Advances in Service Robotics, Vienna, Austria, 

July 7, 2006 

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Concept 

 

(+/- 1.57 rad) 

HLPR Chair is shown in the powered 

chair configuration with controls that the 

patient can use to drive the chair or a 

nurse/caregiver can use the controls 

from behind the chair to mobilize the 

patient. 

Top view of the HLPR Chair rear 

steering and drive wheel and fixed front 

casters configuration. 

(a) 

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(b) 

(a) HLPR Chair can be used to carry a patient to a chair or toilet, rotate the patient ready 

to place them on the seat, remove the footrest, raise the torso lifts and patient above the 

HLPR Chair seat, remove the HLPR Chair seat from beneath the patient, and place the 

patient on the target chair or toilet. (b) HLPR Chair can be used for patient placement on 

a comfortable chair. Additionally, controls can be designed to allow the patient to 

command using voice or remote interface to control the HLPR Chair go away until or 

come when needed. 

Top view showing HLPR Chair accessing a toilet in a bathroom. The red arc shows the 

maximum radius of seat frame rotation needed. 

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HLPR Chair allows lift, currently up to 0.9 m (36 in) above mobility configuration 

height. 

HLPR Chair can be used for patient rehabilitation and incorporate future legs load 

control. 

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Prototype 

 

3D imaging camera 

Color camera 

Load washer (future) 

Outer L-Frame 

 Inner L-Frame 

Rotation point 

Torso lifts 

Patient controls 

Retractable seat 

Retractable footrest 

Lift Actuator 

Casters 

Steel forklift frame Wheel encoders (1 of 2) 

Rear Casters (only for anti-tip) 

Drive/Steering motors and wheel 

Batteries 

Photograph 1 of the HLPR Chair prototype. 

 

Photograph 2 (left) of the HLPR Chair in the mobility configuration showing the side 

view and Photograph 3 (right) front view relative to a typical doorway. 

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Graphic showing the concept of placing a patient onto a toilet or chair with the HLPR 

Chair. The patient drives to the target seat (left), manually rotates near or over the seat 

(middle) while the torso lifts support the patient and the seat retracts, and then is lowered 

onto the seat - toilet, chair or bed (right) 

Photographs 4, 5, and 6 (lt. to rt.) of the HLPR Chair prototype in the same 

configurations as in the graphic above placing a patient on a toilet. 

 Photograph 7 of the HLPR Chair prototype shown in the patient lift position. 

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Computer 

Computer 

interface 

electronics 

Existing 

Nurse controls 

and main relay 

electronic box 

Encoder (1 of 2) 

Photograph 8 of the HLPR Chair with recently added front wheel encoders, development 

computer and interface electronics. 

Padded Torso 

Lifts for under 

arms 

Seat and Footrest 

are retracted 

behind patient. 

Accessible 

controls 

Open frame base 

for walking 

Photograph 9 of the HLPR Chair prototype in the rehabilitation/walking configuration. 

Summer Interns (Alex Page and Robert Vlacich) demonstrate the patient and nurse 

configuration as part of their official duties. 

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Specifications 

Size: 

 Mobility Configuration 145 cm long x 58 cm wide x 178 cm high 

 (57” long x 23” wide x 70” high) 

 with 57 cm (22 1⁄2”) seat ht. above floor 

 Full Lifted Configuration 145 cm long x 58 cm wide x 241 cm high 

 (57” long x 23” wide x 95” high) 

 with 125 cm (49”) seat ht. above floor – currently 

 can be adjusted to lift 91 cm (36”) 

Weight (unloaded) 136 kg (300 Lbs.) 

Payload: 136 kg (300 Lbs.) (designed) 

 91 kg (200 Lbs.) (tested to date) 

Tilt 0.06 rad (10 deg) 

Max. Speed 0.7 mps (28 ips) 

Turning Radius 86 cm (34”) centered about the rider 

Chair Rotate Angle 0.5 rad (90 deg) CCW to 1 rad (180 deg) CW 

Wheels: 

 Rear Drive/Steer 10” diameter pneumatic 

 Front Caster 5” diameter solid 

Ground Clearance 4.4 cm (1 3⁄4”) 

Battery 2-12Vdc dry cells (series 24V) 

Per-Charge Range unknown to date 

Battery weight 11.6 kg (26 Lbs) each 

Drive Train 1 motor chain drive, 1 gearmotor direct steer 

Battery Chargers two (one per battery), off-board 

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Mechanical Design 

Manual Fork Lift Base Frame1

Hydraulic Lift 

 Foot operated hydraulic pump makes raising the load a simple task. 

 Foot pedal release results in controlled lowering to reduce the risk of accidents. 

 Wheels are on swivel casters and lock into position for load lifting and lowering. 

 Two forks lower to 10.8 cm (4.3 in) above the floor and raise loads up to 137 cm (54 

in) to get your machinery or heavy objects at an accessible level. 

 227 kg (500 Lbs) capacity. 

For the HLPR Chair Design, the hydraulic piston was replaced with an electric ball screw 

actuator with 454 kg (1000 Lbs) lift capacity and 0.45 m (18 in) stroke. The fork lift 

chain design allows a 2:1 lift height for 0.9 m (36 in) fork (chair) lift with half the 

payload or 227 kg (500 Lbs). 

 

1

 NIST does not endorse products or organizations. 

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Left (side) view shows 0.9 m (36 in) base and seat frame travel and maximum system 

height. Center side view shows 37.4 cm (95 25/32 in). Center (side) and right (back) 

views show only the base frame with the forklift frame components with the seat frame 

removed and the rotation (top) joint view. 

Side and front views of the HLPR Chair with minimal dimensions for length, height, and 

width while in the mobility configuration. 

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HLPR Chair side view without the rear drive system and suggested front wheel extension 

to allow the seat rotation point to be within the wheelbase. This modification was not 

added to the prototype and is not necessary with appropriate counterweight (e.g., drive 

and battery system) added to the rear. 

(a) 

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 (b) (c) 

Top views of the HLPR Chair showing (a) Maximum length and width, (b) minimum 

HLPR Chair rotation about the front casters axle center 76 cm (30 in) and (c) top view of 

the HLPR Chair. 

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HLPR Chair Component Labels 

These labels refer to drawings that follow. 

Frames pivot 

Seat frame 

assembly 

Base frame 

assembly 

Torso lifts 

Joystick 

Seat (rotated to 

standing position) 

Seat support 

Lift plate 

Forklift frame 

Upper motor 

support plate 

Battery 

Lower motor 

support plate 

Axel plates 

Wheel assembly 

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38 cm 

20.3 cm 16.5 

cm 

5.1 

cm 

10.1 cm 

29.2 cm 

33.0 cm 

40.6 cm 

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37.0 cm 

40.6 cm 

20.3 cm 3.8 cm 

10.1 cm 

5.1 

cm 

29.2 cm 

33.0 cm 

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Top axel plate 

Side axel plate 

(1 of 2) 

Wheel / tire 

Sprocket 

Bearing (1 of 2) 

Coupling nuts 

(1 of 4) 

Front view of wheel assembly 

(component drawings for this assembly follow) 

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11.9 cm 

18.3 cm 

3.5 cm 

0.8 cm 

3.8 cm 

3.8 cm 

7.6 cm 

1 cm 

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10.2 cm 

0.8 cm 

5.6 cm 

11.9 cm 

0.5 cm 

15.2 cm 

14.8 cm 

0.5 cm 

1 cm 

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11.9 cm 

10.1 cm 

7.0 cm 

3.8 cm 

1 cm 

1.9 cm 

3.8 cm 

15.2 cm 

1.7 cm 

1 cm 

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5.1 cm 

5.1 cm 

3.8 cm 0.8 cm 

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14.6 cm 

13.3 cm 

1.6 cm 

1.27 cm 

1.3 cm dp 

1.6 cm dia. 

3.8 cm 

Coupling nut 

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Replaced steering motor with 93 W (1/8th Hp) gearmotor. 

(86 cm/sec) 

29.2

cm

2.5 cm squ. alum. posts (4 each) 

80.5 

cm Speed reducer mount 

(following drawing) 

See Top Axel 

Plate Cutouts 

drawing. 

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Top view of battery compartment. 

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Rear Cover

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See Modifications to Existing Design section for new version of the seat frame assembly. 

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See Modifications to Existing Design section for new version of the base frame assembly. 

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See Modifications to Existing Design section for new version of the frames pivot. 

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Modifications to Original Designs 

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This drawing provided courtesy of McMaster-Carr. Other manufactured turntables could also be 

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 Electrical Design 

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Towards Autonomous Control 

Refer to Photograph 8 for the following design drawings in this section. 

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Stability Testing 

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Prototype Cost Estimate 

Item Manufacturer/Vendor no. each unit cost cost 

Lift Actuator 1 286.00 286.00 

Drive motor, 14A, PM Leeson 1 155.26 155.26 

Steering motor, 1/8 hp Leeson 1 285.00 285.00 

Amplifiers Servo Systems 3 295.00 885.00 

Gear Reducers, couplings McMaster Carr 2 321.60 643.20 

Lubricant McMaster Carr 1 27.70 27.70 

Seat Actuator, 12" McMaster Carr 1 294.74 294.74 

Footrest Actuator, 3" Firgelli 1 80.00 80.00 

Torso Lift Actuator, 3" Firgelli 2 80.00 160.00 

Arm pads - foam, vinyl JoAnn Fabrics 1 20.00 20.00 

Seat, Backrest 1 50.00 50.00 

Wheel, tire McMaster Carr 1 33.00 33.00 

chain (unit = per foot) McMaster Carr 3 3.47 10.41 

Sprockets, 1.67, 5.06" McMaster Carr 1 38.33 38.33 

Electrical boxes Lowes 3 13.00 39.00 

Wire 1 100.00 100.00 

Switches 4 40.00 160.00 

Circuit Breakers 5 40.00 200.00 

Joystick 2 300.00 600.00 

Misc. Elect. Parts 1 100.00 100.00 

Fork Lift frame 1 500.00 500.00 

Seatbelt 2 119.99 239.98 

Batteries, 12V, PC925 Odyssey 2 100.00 200.00 

Battery, 12V, 10Ah 1 25.35 25.35 

Shops work** NIST 1 5,000.00 5,000.00 

Misc. Parts - bolts, etc. 1 200.00 200.00 

total: $ 10,332.97

** Shop work for this prototype was dramatically reduced incorporating a redesigned seat 

and base frame through the use of bent tubing (see Modifications to Original Design 

section). The base frame was made from 5 cm (2 in) OD steel electrical conduit with a 

welded support bead and the seat frame was designed at NIST and procured from a pipe 

bending manufacturer. A 30 cm (12 in) diameter turntable bearing ring was used as the 

rotation device. The total for these components was approximately $400.00 verses 

$5,000.00. 

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