eXperimental Kinematics Lab (XKL)

Mechanical Engineering
The Pennsylvania State University, University Park, PA 16802
H.J. Sommer III (hjs1-at-psu.edu)

Current Projects

Unmanned Aicraft for Agricultural Applications
H.J. Sommer, R.M. Crassweller, J.E. Kamininski, T.T. Lulis - State Horticultural Association of Pennsylvania
We are building a knowledge base and technology infrastructure to facilitate collaboration between plant scientists, engineers, growers and government. Our goal is to help scientists and farmers use unmanned aircraft to increase crop yields, reduce production costs and prevent exposure to tedious or hazardous work environments.

Map to Test Facility - Lat,Lon = 40.704927,-77.963771 APD map

Ag Progress Days - August 10-12, 2021

Prior Projects

Dual Beam Slip Resistance Sensor
H.J. Sommer -
Current methods to measure slip resistance of shoes on flooring have limited reproducibility under wet or dusty contaminated conditions. This project designed a strain gage slip resistance sensor to simultaneously measure normal force and friction force under a friction coupon in contact with flooring. Design goals are manual operation and reliable estimation of slip coefficient. Current work focuses on validation against existing slipmeters and on industrial design for commercialization.
Experimental Angular Velocity, Acceleration and Jerk from Landmark Trajectories
H.J. Sommer, N. Okita
Least-squares methods were developed to determine the Instantaneous Helical Axis (IHA) for angular velocity and instantaneous angular acceleration and angular jerk from experimental measurement of landmark trajectories. These algorithms are used in biomechanics to determine rotation of body segments from photogrammetric measurement of markers attached to the segments. Additionally, relative kinematics between segments and instantaneous invariants of motion were defined. The algorithms were computationally and experimentally validated using an RSUR spatial mechanism.
RSUR ISA first and second pitch Axode

Superquadric Modeling of Pediatric Positional Plagiocephaly
H.J. Sommer, M.A. Dias
Sponsor - Woodward Foundation
The occurrence of positional plagiocephaly in infants has increased dramatically since 1992 when back sleeping was recommended to reduce Sudden Infant Death Syndrome. In positional plagiocephaly, crania of infants may mold asymmetrically under gravity loading if their heads are routinely positioned in the same orientation. Unfortunately, clinical evaluations of plagiocephaly are still qualitative and treatment outcomes are concomitantly difficult to document.

To address these measurement problems, a new method for quantifying cranial shape and asymmetry has been developed to fit symmetric superquadric geometric models to three-dimensional (3D) coordinate measurements from cranial surfaces. Cranial surface asymmetry can then be quantified by deviation of the surface measurements from the inherently symmetric superquadric model. Superquadric parameters have simple geometric interpretation, are very reproducible and can be statistically significant indicators of cranial shape.
Before treatment Before treatment
After treatment After treatment

Cranial Map of Scalping Artifact
G.R. Milner, H.J. Sommer
Three-dimensional measurements of knife cut marks on multiple dried skulls were digitized and mapped onto standard cranial models to help identify patterns used during scalping.
Oblique views Polar plots

Farm Tractor Stability Systems to Improve Operator and Mechanical Performance
D.J. Murphy, P.J. Garvey, S.N. Brennan, H.J. Sommer
Sponsor - NIOSH New York Center for Agricultural Medicine and Health (NYCAMH)
The objective of this research is to reduce the number of deaths and injuries caused by farm tractor overturn through the development of technology-assisted training and tilt alerting tools for tractor operators, and through mechanical tractor overturn intervention. To accomplish this objective, we propose four specific goals centered about one key question: Can tractor overturns be prevented using cost effective and readily implemented technology?

Goals 1-3 focus on: a) understanding the causation of tractor overturn by probing operator psychology; and b) reducing exposure to side overturns through operator intervention by introducing tractor tilt sensors and display systems alerting drivers to excessive tilt. Goal 4 focuses on low cost commercially available tilt sensors and the industry standard CAN bus (an in-vehicle communication device installed in most tractors) for active mechanical or engineering intervention of rear overturn.
Old roll simulator LTI simulator Deere cab faceLab eye tracking

Overturn images and movies

Slip Sensing for Robot Feet
H.J. Sommer, N. Okita
Sponsor - Honda
A novel foot slip sensor is proposed to help predict loss of traction under the feet of walking robots. The sensor will use a Kalman filter and simple inertial measurement unit (IMU) to identify slip when the covariance of MEMS angle and angular rate sensors exceeds a threshold. This concept can assess stable landing of the foot as well as monitor the stance phase of loading. It may also be able to measure impending macroslip by microslip of compliant sole material.
Slip model Drag sled Stick-slip data

Overturn Stability and Traction Control of Unmanned Ground Vehicles
H.J. Sommer
Sponsor - U.S. Army Engineer Research and Development Center (ERDC) Cold Regions Research and Engineering Lab (CRREL)
A new generation of unmanned ground vehicles (UGV) have been developed for military, hazardous environment and construction applications. While removing the human operator from the vehicle increases safety of the operator, it dramatically reduces safety of the vehicle. In particular loss of lateral traction and front/side overturn are problematic because the operator no longer has vestibular and kinesthetic feedback to assess vehicle stability. They can no longer feel vehicle attitude, vibration and motion "by the seat of the pants". Newer high speed UGVs further exacerbate stability problems. This project will address low-cost MEMS sensors that can help UGV operators better monitor vehicle stability and traction.
Rear overturn model Side overturn model Lateral slip model

Body Position Recorder for Sleep Apnea
L. Sweer, H.J. Sommer
Sponsor - CIHDS
Measure body roll angle during sleep
BPR data BPR circuit board BPR strap

Solid Strut Motion Platform
H.J. Sommer
Sponsor - NSF, NIST
Stewart-Gough platforms use six extensible struts between the base and platform to control six degrees-of-freedom (DOF) of platform motion. Traditional applications include ride simulators and mulitaxis machining. A novel solid strut platform (SSP) was constructed to investigate workspace/velocity design constraints and vibration suppression using redundant Stewart-Gough actuators. Current work addresses conversion to MEMS scale.

Portable Biomechanical Assessment Suite (PBAS)
H.J. Sommer
Sponsor - NIOSH Morgantown
The ultimate goal of this project is to help reduce the incidence of musculoskeletal disorders related to occupational lifting. While laboratory methods in biomechanics have been developed to predict musculoskeletal forces during lifting, input data (body motion and external forces applied to the body from the floor and payload) require special instrumentation that is not portable to the workplace.

The specific goal of this project is to develop a prototype suite of sensors that can be worn in the workplace to quantify repetitive loading on the lower back (magnitude of forces and their time history) during occupational lifting during a given work day. This loading information can then be used to develop intervention strategies. A prototype Portable Biomechanical Assessment Suite (PBAS) will be developed to measure body motion and external loading in unstructured field conditions. The PBAS will be able to be worn unobtrusively by a worker during a normal work day.
video Dynamic model Planar IMU

Instrumentation for Farm Tractor Overturn
D.J. Murphy, H.J. Sommer
Sponsor - NIOSH
Although roll-over protection systems (ROPS) are now mandated for farm tractors, tractor overturns cause approximately 400 deaths per year in the United States. This project developed new cost-effective combinations of sensors and microprocessors to detect impending side overturn, overturn of tractors with attached implements and operator display ergonomics and psychology. Click on photos for more details.

FY01 FY01           FY02 FY02           FY03 FY03          

FY04 FY04           FY05 FY05

In-Vehicle Noise Generated By Rumble Strips
E. Donnell, H.J. Sommer, P.J. Garvey
Sponsor - National Cooperative Highway Research Program/Midwest Research Institute
The goal of this project was to assess the efficacy of current rumble strip designs. A sound-level meter (SLM) and GPS unit respectively measured in-vehicle noise and vehicle motion (speed and angle of departure) while passenger cars were driven onto rumble strips in the road shoulder at highway speeds. Approximately 1000 locations in six different states were tested and sound level was correlated to strip length/width/depth/spacing and vehicle speed.
Microprocessor Assessment of Postural Stability and Tremor
H.J. Sommer
Repeatable measurement of postural stability during quiet standing is particularly important to assess proclivity to falling in the elderly and to monitor postural effects of peripheral neuropathy in the diabetic foot. Unfortunately, traditional methods to assess postural stability such as timed stance tests and force plate center-of-pressure (COP) measurements are either subjective or expensive and not portable. To this end, dual axis MEMS accelerometers have been interfaced to microcontrollers to record supracranial accelerations and compute postural stability indicators. The same hardware is being adapated to quantify temor for assessment of neurological disorders.
Identification of Dynamic Nonlinearities in Robots for Predictive Maintenance
H.J. Sommer
Sponsor - PSU ARL
Identification of dynamic nonlinearities in robot joint drives using the Hilbert transform and internal excitation is being studied for predictive maintenance. Over long periods of operation, backlash and Coulomb friction in joints increase due to wear. If these nonlinearities can be monitored at periodic intervals, robot maintenance schedules can be predicted more reliably. The differences between the Fourier and Hilbert transforms of joint drive performance on a SCARA industiral manipulator were correlated to artificially induced changes in backlash and friction. Numerical simulations, experiments on a simple spring-mass-damper and experiments on a prototype two-link manipulator have shown that Fourier versus Hilbert transform differences can identify the presence, magnitude and location of changes in Coulomb friction.
Locomotion in Microgravity
P.R. Cavanagh, H.J. Sommer
Sponsor - NASA Johnson Space Center
Significant losses in bone density and mineral content in the lower extremities have been reported following prolonged weightlessness. Recent investigations suggest that mechanical influences such as bone loading and strain rate may be critically important to stimulate new bone formation. A ground-based microgravity simulator was developed to investigate which factors affect limb loading during tethered treadmill exercise. The microgravity simulator incorporates a supine suspension system, an instrumented vertical treadmill and a gravity replacement harness to load the subjects horizontally into the treadmill. Ongoing tests using the simulator address exercise protocols as countermeasures for hypokinetic osteoporosis. This work supports the Treadmill Vibration Isolation System (TVIS), a free-floating powered exercise treadmill, as part of ongoing Risk Mitigation Experiments (RME) on STS-81 and the International Space Station (ISS).
STS-81 emblem ISS

Measurement of Six Degree-of-Freedom TVIS Motion
H.J. Sommer, P.R. Cavanagh, D.R Lemmon
Sponsor - Krug Life Sciences for NASA Johnson Space Center
The Treadmill Vibration Isolation System (TVIS) is a free-floating powered exercise treadmill designed to mitigate hypokinetic osteoporosis of the lower limbs during prolonged spaceflight. Two studies were conducted to measure all six degrees-of-freedom (6DOF) of TVIS motion during use on STS-81 and during ground tests at NASA Houston. Measurement of TVIS motion on STS-81 employed nonlinear stereophotogrammetry using sequences of video images from camcorders. Ground tests used a novel 6DOF Instrumented Spatial Linkage (ISL) developed and constructed at Penn State.
TVIS on STS-81 ISL TVIS emblem

Sling Forces on Aircraft Caused by External Payloads
H.J. Sommer, J.M Cimbala
Sponsor - Boeing Helicopter
Aerodynamic drag on external payloads carried by slings under aircraft can impair aircraft handling and reduce stability, particularly due to self-excited limit cycle yaw oscillations (SELCYO) of the payload. Laboratory wind tunnel drag test data from scale models of typical external payloads were combined with analytical modeling of sling motion to predict sling forces and yaw instability. The predictions were validated by wind tunnel tests of scale models of external loads suspended with scaled slings.
V22 Osprey V22 lifting HMMWV V22 flying with HMMWV V22 lifting howitzer

Directed Seismic Vibration for Crowd Dispersal
H.J. Sommer
Sponsor - ARL Institute for Non-Lethal Defense Technology
A feasibility study of inducing ground vibration to disperse crowds was conducted. Capabilities of commercial-off-the-shelf (COTS) technologies including vibroseis trucks used in geological prospecting and industrial compactors and breakers used in heavy construction were compared to seismic vibration levels required to frighten personnel yet not cause collateral damage to pavement and structures.
Vibroseis truck vibration compactor

Standardized Testing of White Food-grade Belts
P.N. Walker, H.J. Sommer, M. Toda
Sponsor - Hershey Foods
An industry survey of current ASTM, ISO, DIN and internal test standards was used as a basis for competitive evaluation of belt suppliers.
In-vivo Poroelastic Material Properties of the Subcalcaneal Pad
H.J. Sommer, P.R. Cavanagh
Finite element analyses (FEA) of the foot/shoe interface require accurate material properties. This project was a pilot study to use DANTE MRI to visualize a tagged grid within the subcalcaneal fat pad before a known surface loading was applied. Numerical comparison of the deformed DANTE grid to homologous FEA deflections allowed iterative estimation of in-vivo material properties using Levenberg-Marquardt algorithms. The technique was validated on hyperelastic foam coupons.
foam original foam deformed

Three Dimensional Normative Databases of Muscle Origins and Insertions of the Lower Extremities
H.J. Sommer, T.M. Kepple
Sponsor - NIH
In-vivo lines of action for muscles can be predicted by filming the motion of external markers attached to palpable landmarks on subjects during locomotion. This requires a database of three-dimensional (3D) locations of muscle origins and insertions relative to palpable landmarks. Unfortunately, the number of skeletal specimens used to accumulate existing databases of 3D origin and insertion locations for the lower extremities were relatively limited. To this end, 3D locations of muscle attachments on the pelvis, femur, tibia/fibula, and foot were accurately digitized for 52 dried skeletal specimens from the Terry Collection of the Smithsonian National Museum of Natural History. Thirteen specimens each were selected within four gender/race categories with representative stature. Normative 3D databases developed from these landmark data statistically extend currently available 3D databases by an order of magnitude. These new data better describe expected gender/race variation and provide better effective lines of action for muscle which wrap over boney structures.
Single Beam Laser Vibrometer
H.J. Sommer, M.W. Trethewey
Sponsor - NSF
Prior work on multiple beam laser vibrometers for simultaneously measuring range, pitch and roll of a moving reflective target was extended to use a single laser beam and two transparent position sensing photodetectors. Calibration of the new single beam vibrometer with traditional Marquardt methods and with artificial neural networks compared favorably to previous dual beam vibrometer precision and accuracy. Additional electronics were developed to modulate the laser beam and remove the effects of background illumination.
Machine Vision Inspection of Apples, Potatoes and Mushrooms
P.H. Heinemann, C.T. Morrow, H.J. Sommer
Sponsor - State Horticultural Association of PA
A variety of novel lighting techniques and machine vision algorithms were developed to grade apples, potatoes and mushrooms. Grading was based on optical inspection and numerical quantification of overall shape, size, color and surface blemishes. The shape/size/color/blemish data were then combined to assign an overall quality grade. Traditional linear classifiers, expert system rules and artificial neural networks methods for assigning grades were compared to USDA inspectors with excellent correlation. Laboratory hardware and PC based software were upgraded for on-line field use.
Adjustable Prosthetic Sockets using Shape Memory Alloys
H.J. Sommer
Between 60 to 80 percent of amputees typically report inadequate fit between their residual limb and their prosthetic sockets particularly as the residual limb atrophies. While this lack of fit can be addressed by thicker and thicker stump socks, many amputees require adjustment or complete replacement of the socket every two to five years. This project demonstrated the technical feasibility of using socket walls with embedded Nitinol shape memory alloy wire. The wire was stretched to ten percent plastic elongation before being wrapped around the outer socket wall. Subsequent electrical heating of the wire was able to produce four percent diametral reduction of the socket to allow on-line refitting