DEVELOPMENT OF A MOBILE MANIPULATOR 

TO REDUCE LIFTING ACCIDENTS

Objective 

 Develop a mobile manipulator that one person can use to lift 

and maneuver 50- to 600-pound loads. It can be used in maintenance shops and mines to reduce lifting accidents (Figure 1 and 2). 

Background 

 Lifting heavy items is one of the leading causes of injury in 

the workplace. Mine Safety and Health Administration statistics 

showed that, in 2004, back injuries accounted for over 20% of 

all injuries (1,699 cases) and resulted in 110,000 lost days of 

work. Forty-one percent of those injuries resulted from 

materials-handling or maintenance activities.1

 In addition to 

back injuries, lifting injuries include hernias, ruptures, sprains, 

and strains resulting from losing control of the item being lifted. 

Factors associated with accidents are weight of the item being 

lifted, awkward postures, inadequate handholds, and the working 

environment itself.

 High accident rates were noted when lifting items that 

ranged from 50 to 600 pounds, particularly in tight working 

quarters where maneuverability was critical. Research indicated 

that a mobile lifting arm would eliminate many lifting accidents 

in environments where other lifting devices (fork lifts, overhead 

cranes, mobile A-frames) would not be practical. 

 NIOSH has built a first-generation mobile manipulator unit 

designed to be used on hard, level floors such as in a shop. The 

complexity of motion, number of moving parts, compact design, 

and design constraints of the manipulator required advanced 

computer-aided design work (Figure 3). As a result of the design 

work, thirty-eight claims are included in the patent applications. 

NIOSH will be conducting field trails and working with 

manufacturers to put the manipulator into industrial use. 

Operating the Mobile Manipulator 

 The mobile manipulator is a self-propelled, battery-powered 

lifting arm mounted on a central turret that allows full rotation. 

_____________ 1

Mine Safety and Health Administration. (2004) Mining Industry Accident, 

Injuries, Employment, and Production Statistics. Available from 

http://www.msha.gov/ACCINJ/accinj.htm 

Figure 1.—Manipulator in operation. 

To operate, a worker trams the unit into position for the lifting 

task and deploys stab-jacks for leveling and stabilizing. The 

linkage system is designed to allow the operator to guide heavy 

loads precisely; for example, sliding a 200-pound gear assembly 

onto a shaft where alignment and damage to equipment are 

critical considerations. Although the operator needs only 10 

pounds of pressure to lift the load, the momentum of moving the 

load can create a need for braking, and so the operator has hand 

brakes to stop arm and turret movement immediately. The ease 

of tramming and steering, along with the small size of the 

manipulator, allows operators to stow the unit conveniently close 

by without interfering with ongoing operations. 

For More Information 

 To obtain more technical information about the mobile 

manipulator or inquire about becoming involved in the manufacturing phase of development, contact Eric Zahl or Curtis 

Clark at (509) 354-8000 or fax to (509) 354-8099; e-mail 

EZahl@cdc.gov or CCClark@cdc.gov; or mail to Eric Zahl, 

NIOSH Spokane Research Laboratory, 315 E. Montgomery 

Ave., Spokane, WA 99207. 

No. 521 December 2006 
Design Features 

 • Mobile with multiple speeds for tramming and 

 turning 

 • Compact and easy to stow or transport underground 

 • Full range of motion for ease of maneuvering objects 

 • Lifting pressure felt by operator limited to 10 pounds 

 • Operator positioned near lifting to control movement 

 • Leveling and stability provided by jacks 

 • Gripping attachments for specific tasks 

 • Power choices: on-board battery, compressed air, or 

 110-V cords 

 • Braking on lifting arm for load control 

Specifications 

Vehicle 

Weight 2500 lb 

Length 64 in 

Width-tram 32 in 

Width-oper 44 in 

Height-tram 77 in 

Height-oper 97 in 

Speed slow 1/2 mph 

Speed fast 2 mph 

Drive system Hydraulic 

Gradability 15% 

 

Manipulator 

Lifting cap-hook 600 lb 

Arm vertical reach 41 in 

Arm horizontal reach 50 in 

Arm turret rotation 360N

Op. sys Pneumatic 

Op pressure 90 psi 

To receive other information about occupational safety and 

health topics, call 1–800–35–NIOSH (1–800–356–4674), or 

visit the NIOSH Website at www.cdc.gov/niosh 

Mention of any company name or product does not constitute 

endorsement by the National Institute for Occupational 

Safety and Health. Figure 3.—Design specifications.

DHHS (NIOSH) Publication No. 2007–111

 Figure 2.—Manipulator shown loaded with stabilizers activated.