Catepillar Exosuit Loadlifters

The Caterpillar P-5000 Exosuit Loadlifter, commonly referred to as a Power Loader, is a commercial mechanized exoskeleton used for lifting heavy materials and objects. As well as widespread industrial use, the P-5000 is heavily employed by the US Colonial Marine Corps to load ordnance on board their starships. Power Loaders are equipped with hydraulic "claws" that can be used to hold and manipulate a variety of objects.

It is also equipped with welding torches, and sometimes can use weapon attachments.

## Overview

Configured as an anthropomorphic exoskeleton power frame, the P-5000 offers unprecedented flexibility when handling ordnance and cargo during rough field operations. It also serves as a platform for conducting heavy maintenance away from fixed workshops. The Power Loader is able to multiply a human operator's strength and lifting capacity several thousand times and is capable of manipulating loads up to 4,000 kg. The P-5000 is a rugged and reliable alternative to conventional forklifts, rigs and cranes.

The chassis of the P-5000 consists of a reinforced steel framework with two upper load bearing points for the arms. A hydrogen fuel cell is mounted on the back of the frame, providing up to 65 kW of power for the loader. The articulated legs are attached by two semi-universal bearings on either side of the base of the chassis, allowing up to 60 degrees of 'x' axis (hip swivel) movement; just below these are a set of knee bearings. Leg motions at the hip are controlled by a pair of 20 kW linear motors actuated via a fast-feedback loop slaved to the operator's movements. Below the hip, hydraulic actuators extend from the main load-bearing points to the aft sections of the legs, providing 'z' axis (fore/aft) movement at the knee joints while pitch control is handled by a second series of actuators at the ankles. To prevent toppling while stationary and under load, the chassis is gyrostabilized. These gyros can be rotated rapidly out of phase in order to 'decouple' the chassis stabilization system along the determined axes of motion and provide the necessary instability required for bipedal movement. For very heavy lifting work, additional stability can be provided by bolting up to 250 kg of concrete ballast to the underside of the chassis.

The loader's arms are attached to the very top of the chassis by a pair of complex universal bearings stressed to operate under loading of up to 4,000 kg. Arm motions in the 'y' and 'z' axes are controlled by linear motors while movement in the 'x' axis and at the elbows is powered by a series of hydraulic actuators. The limbs mount a set of vice manipulators that are capable of full 360° rotation. Most common industrial storage mediums are fitted with uniform, purpose-made grips than can easily interface with the P-5000's claws. Typically, one fork of each vice is placed under the object to be lifted while the other fork clamps down on top of the object, holding it firmly and securely. Manipulator function is controlled from an operator handgrip/joystick combination situated on the inside of each limb. Attachment points for additional tools (such as cutters and welders) are located on the manipulators.

## Operating Controls

To work a Power Loader, an operator first backs into the machine, buckling themselves in with the webbing harness. A roll cage is pulled down to provide protection for the head and torso, while feet are secured with straps. Power up and system diagnostics are handled by a punch keypad built into the operator's handgrips. This keypad also controls any additional external tools fitted to the machine.

When powered up, the P-5000 is slaved to the operator's limb movements, duplicating their walking and lifting motions almost exactly. Response time to operator input is almost instantaneous, while sophisticated computer controls dampen any system induced 'twitches' or oscillations that arise out of involuntary operator movement. Problems are only likely to arise if the loader is walking or reaching at full extension, as the system is likely to enhance movement beyond the fine-tuning capabilities of the operator; standard operating procedures typically forbid operators from performing such maneuvers.

If operating over rough ground, the Power Loader will provide feedback cues to the operator to help them keep his or her footing. However, owing to the P-5000's high lifting capacity and relatively small foot area, operations with very heavy loads on soft ground are not recommended, as the extreme downward pressure generated underfoot can cause the unit to literally bury itself in the ground. Automatic lockout systems will generally prevent any movement that will topple the loader, and the system has generally proved safe to use over all but the most treacherous terrain. As with any lifting device, there are strict guidelines regarding weight limits that the loader can handle.

Though simple in principle, considerable practice is required to use a Power Loader efficiently and safely, and the equivalent of a Class 2 civilian cargo handling license is needed to operate in USCM service. Operators must become used to the loaders mass and its tendency to 'lead' the operators movements. Operators must be careful not to overcompensate for this tendency, otherwise they may induce unwanted oscillations into the control systems. Operating a P-5000 requires sureness and economy of movement, since hesitancy and exaggerated motion tend to place undue stress on the load-bearing joints. Training to use a Power Loader takes about six weeks of simulator training and 'hands-on' experience, though this is extended to eight weeks to qualify USCM personnel and includes training in rough field operation.