Title: Robotics Research: Spatial Mechanism Design and Analysis and Autonomous Vehicle Development
1Robotics ResearchSpatial Mechanism Design and
Analysisand Autonomous Vehicle Development
- Carl D. Crane III
- Professor, Department of Mechanical and Aerospace
Engineering - Director, Center for Intelligent Machines and
Robotics - University of Florida
2Agenda for presentation
- Introduction
- Spatial Mechanism Design and Analysis
- passive and active force control mechanisms
- controlled compliance
- self-deployable tensegrity structures
- Autonomous Vehicle Development
- ground vehicle technologies
- architecture design
- micro-air vehicles
3Introduction - Univ. of Florida
- The University of Florida is a public,
comprehensive, land-grant, research university. - It is one of only 17 public, land-grant
universities that belongs to the Association of
American Universities. - 46,500 students
- 72 undergraduate
- 28 graduate
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5Introduction - College of Engineering
- 11 Departments
- 4,500 undergraduate students
- 1,900 graduate students
- degrees granted in 00-01 academic year
- 726 Bachelor
- 465 Master
- 95 Ph.D.
6Introduction - CIMAR
- Interdisciplinary robotics research group founded
in 1970s by Dr. Del Tesar. - Directorship changed to Dr. Joseph Duffy in 1987.
- Currently consists of 3 faculty and 28 graduate
students. - 35 Ph.D. graduates and 70 M.S. graduates in
period 1985-2000.
7Introduction - CIMAR
- Joseph Duffy
- graduate research professor
- fellow ASME
- received ASME Machine Design Award in September
2000 for "eminent acheivement in the field of
machine design"
8Agenda for presentation
- Introduction
- Spatial Mechanism Design and Analysis
- passive and active force control mechanisms
- controlled compliance
- self-deployable tensegrity structures
- Autonomous Vehicle Development
- ground vehicle technologies
- architecture design
- micro-air vehicles
9Passive force control mechanisms
- Industrial robots are typically six degree of
freedom devices. - The torque of each actuator is
- commanded by controlling current.
- Closed loop joint position control
- is typically enacted by using
- optical encoders to provide
- feedback.
10Passive force control mechanisms
- Simple applications or industrial robots are
- position control operations where the manipulator
does not contact the environment - spray painting
- welding
- force control operations
- where the end effector
- is constrained so it
- cannot move
11Passive force control mechanisms
- Research objective
- develop a means whereby the end effector of a
serial robot manipulator can be controlled for
position and force - Approach
- design and implement a compliant wrist mechanism
12Planar example
- it is desired to control the contact force of a
wheel as it moves along a rigid wall - the wheel is connected to a simple 2 degree of
freedom serial manipulator by a two-spring system
the lengths of the springs are measured - input parameters are ?d1 and ?d2, the change in
displacement of the end effector - output parameters are ?fx and ?fy, the change in
force at point C
13Planar example
- the relation between (?d1, ?d2) and (?fx, ?fy)
can be written as
14Planar example
- numerical example
- ?1 45, ?2 90
- k1 k2 10 lbf/in
- system is at unloaded position
- determine how to move robot end effector (?d1,
?d2) in order to reduce the normal contact force
fn by some amount ?fn
15Planar example
16Planar example
- the relationship between change in displacement
and change in force can be written as - inverting K gives
17Planar example
- at this instant
- thus
- at this instant, the normal force can be adjusted
by translating the end effector in the x direction
18Second planar example
- control of force and moment
- a passive three-spring system is inserted in the
wrist of the manipulator - spring lengths are measured
- the relationship between the joint displacements
and the wrench (force/ torque) applied to the end
effector can be determined
19Spatial passive force control mech.
- Develop a passive 6 d.o.f. parallel mechanism to
use as a wrist element on an industrial
manipulator. - Platform is comprised of 6 S-P-S leg connectors.
- Leg lengths are measured.
- Spring constants and
- spring free lengths are
- measured experimentally
- during calibration.
- Relationship between dis-
- placement of top platform
- relative to the base and the
- applied wrench can be determined.
20Determination of platform geometry
- The platform geometry must be such that a forward
displacement analysis can be readily conducted. - If the lines along each of the legs become
linearly dependent, the platform is in a
singularity and will collapse. - For arbitrary loading, at the nominal home
position, the device should be as far from a
singularity as possible.
21Determination of platform geometry
- The platform with the simplest forward analysis
is the 3-3. - Forward analysis reduces to a 4th order
polynomial in t2.
- The problem with this geometry lies in the
co-intersecting ball-and-socket joints.
22Determination of platform geometry
- The 6-6 platform avoids the co-intersecting joint
problem, but the forward analysis is complex.
23Determination of platform geometry
- The special 6-6 platform was discovered.
- avoids the co-intersecting joint problem
- complexity of forward analysis is same as for the
3-3 platform
Note that at the mechanism is in a
singularity for the configuration shown in the
figure.
24Special 6-6 platform geometry
25Determination of platform geometry
- The platform geometry must be such that a forward
displacement analysis can be readily conducted. - If the lines along each of the legs become
linearly dependent, the platform is in a
singularity and will collapse. - For arbitrary loading, at the nominal home
position, the device should be as far from a
singularity as possible.
26Determination of platform geometry
- For 3-3 platform
- optimal home position occurs when the base is
twice the size of the top platform (b 2a) and
the distance between the platforms is a. - similar analysis performed for special 6-6
a
a
b
27Hardware development
- Prototype device fabricated.
28Agenda for presentation
- Introduction
- Spatial Mechanism Design and Analysis
- passive and active force control mechanisms
- controlled compliance
- self-deployable tensegrity structures
- Autonomous Vehicle Development
- ground vehicle technologies
- architecture design
- micro-air vehicles
29Active force control mechanism
- development of parallel platform mechanism with
actuated prismatic joints - force in each leg sensed
- position and orientation of top platform
determined from measurements of a separate
metrology frame
30Active force control mechanism
- system being designed to manipulate a 250 lbf
load - control system will aim to move the top platform
in response to externally applied wrenches to the
top platform
31Active force control mechanism
32Agenda for presentation
- Introduction
- Spatial Mechanism Design and Analysis
- passive and active force control mechanisms
- controlled compliance
- self-deployable tensegrity structures
- Autonomous Vehicle Development
- ground vehicle technologies
- architecture design
- micro-air vehicles
33Controlled compliance
- a semi-active piezoelectric based friction damper
is being incorporated into a leg connector to
allow for control of motion damping in the leg
Actuator
Air Bearing
Spring
Friction Pad
34Agenda for presentation
- Introduction
- Spatial Mechanism Design and Analysis
- passive and active force control mechanisms
- controlled compliance
- self-deployable tensegrity structures
- Autonomous Vehicle Development
- ground vehicle technologies
- architecture design
- micro-air vehicles
35Tensegrity structures
- comprised of struts in compression and ties in
tension
36Self-deployable tensegrity structures
- certain ties are replaced by elastic members
37Self-deployable tensegrity structures
38Self-deployable tensegrity structures
- analyses conducted to
- determine deployed position at equilibrium
- determine motion of system in response to
externally applied loads - determine motion of system in response to change
in spring free lengths
unloaded and final equilibrium positions
39Application of tensegrity mechanisms
- self-deploying satellite antennae
40Application of tensegrity mechanisms
41Application of tensegrity mechanisms
b
a
c
d
42Agenda for presentation
- Introduction
- Spatial Mechanism Design and Analysis
- passive and active force control mechanisms
- controlled compliance
- self-deployable tensegrity structures
- Autonomous Vehicle Development
- ground vehicle technologies
- architecture design
- micro-air vehicles
43UF systems
44AFRL systems
45Autonomous vehicle technologies
- path planning
- obstacle detection and mapping
- positioning systems
- vehicle control
- system architecture
46Autonomous vehicle technologies
47Autonomous vehicle technologies
- path planning
- obstacle detection and mapping
48Autonomous vehicle technologies
- path planning
- obstacle detection and mapping
- positioning systems
49Autonomous vehicle technologies
follow-the-carrot
pure pursuit
50Vehicle control
follow-the-carrot
pure pursuit
51Vehicle control
- previous two methods only aim to move the vehicle
to the goal point - the desired orientation at the goal point is not
being considered - errors in position and errors in orientation have
different units - led to a new technique called vector pursuit
- determine a screw that will correct translational
error - determine a screw that will correct rotational
error - sum them together to get a desired instantaneous
motion screw
52Vector pursuit - method 1
goal pose
vehicle pose
path
53Vector pursuit - method 1
- the desired screw must be mapped to the allowable
motion space of the vehicle
commanded twist
desired twist
54Vector pursuit - method 2
- take into account vehicle motion constraints when
determining the screw to correct translation and
rotation
path
vehicle pose
55Fuzzy reference model learning control
56Vector pursuit implementation
57Autonomous vehicle technologies
- path planning
- obstacle detection and mapping
- positioning systems
- vehicle control
- system architecture
58System architecture development
- UF is a member of the DoD Joint Architecture for
Unmanned Ground Systems (JAUGS) Working Group - JAUGS goals
- reduce life cycle costs
- reduce development and integration time
- provide a framework for technology insertion
- accommodate expansion of existing systems with
new capabilities
59JAUGS
- the architecture is comprised of a set of
components with well defined interfaces - the components are designed for
- vehicle platform independence
- hardware independence
- technology independence
- mission isolation
60MAX
JAUGS
PLN
MCU
OCU
sweep planner
path seg- ment driver
vector driver
go to goal planner
way point driver
velocity state driver
MRS main
obstacle avoidance
MRS
MRS
POS
DMS
pose sensor
obstacle detection
mapping
velocity state sensor
MRS
MRS
VCU
camera
camera
camera
actuator component
sensor component
primitive driver
video switch
MRS
61Primitive driver component
vehicle independent input message
action description
propulsive wrench resistive wrench
Primitive Driver
effect motion via vehicle actuators
62Wrench
- set of six ordered values
- fx, fy, fz mx, my, mz
- values sent as a percentage
F
mx
x
my
y
mz
z
63example 1 teleoperation
OCU
wrench motion commands defined in local coord.
sys.
Primitive Driver Component
vehicle motion
64velocity state driver component
velocity sensor message
desired velocity state
Current velocity state. vehicle coordinate system
The velocity that the vehicle should have at this
instant (instantaneous motion screw). vehicle
coordinate system
Velocity State Driver Component
wrench motion command
Desired propuslive and resistive force acting on
vehicle. vehicle coordinate system
65example 2 operator specifies velocity state
global coordinate system
OCU
desired velocity state defined in vehicle coord.
system
Velocity State Driver Component
wrench motion commands defined in vehicle coord.
sys.
Primitive Driver Component
Velocity State Sensor Component
vehicle motion
66example 3 autonomous navigation
path defined as a series of waypoints measured in
global coordinate system
Path Segment Driver Component
current goal point defined in global coordinate
system
Way Point Driver Component
vehicle pose in global coord. system
desired velocity state defined in vehicle coord.
system
velocity state defined in vehicle coordinate
system
Velocity State Driver Component
wrench motion commands defined in vehicle coord.
sys.
Pose Sensor Component
Primitive Driver Component
Velocity State Sensor Component
vehicle motion
67Component implementation
68Agenda for presentation
- Introduction
- Spatial Mechanism Design and Analysis
- passive and active force control mechanisms
- controlled compliance
- self-deployable tensegrity structures
- Autonomous Vehicle Development
- ground vehicle technologies
- architecture design
- micro-air vehicles
69micro-air vehicles
- work done by P. Ifju and M. Nechyba of the
University of Florida
70micro-air vehicles
71micro-air vehicles
72Recent Adventure
- The Search for Lewis and Clarks Iron Boat
- 10 - 14 Sep 2001
- Great Falls, Montana
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74Lewis and Clark
75Lewis and Clark Results
76Lewis and Clark
77Lewis and Clark
78Video Presentations
79Conclusion
- Spatial Mechanisms
- Autonomous Ground Vehicles