A down-scaled over-actuated vehicle equipped with
autonomous corner module functionality
Johannes Edrén, edren@kth.se
PhD student at KTH Vehicle Dynamics, SE-100 44 Stockholm, Sweden
This poster presents a functional down-scaled prototype
of a passenger car with capability to control steering,
wheel torques, wheel loads and camber individually. The
chassis technology is based on a modularised platform,
referred to as Autonomous Corner Modules (ACM),
which simplifies the re-use of components at the four
corners of the vehicle and between different vehicles.
Here, an insight in the design of the vehicle and the
selection of electrical actuators and sensors to provide all
ACM functions is given. The 1:6 scaled prototype is later
to be used in vehicle dynamics research.
VEHICLE FUNCTIONS
Steering angles, wheel torque, camber angles
and vertical wheel force/position is
individually controlled.
MOTION CAPABILITIES
Vehicle side slip and yaw rate are decoupled, which gives the possibility to
mimic the planar vehicle behaviour of
most passenger vehicles on the roads today.
In
addition,
since
vertical load can be
individually controlled,
also vehicle roll and
pitch can be mimicked.
Chassis design
The chassis is basically consisting of
two aluminium profiles connecting
all the parts together. The
suspension of each wheel consists
of a single upper A-arm connected
to the wheel hub carrier and to the
spring/damper unit.
Control
The driver input signals are
transferred via a regular radiocontrol system with a transmitter
and a receiver. This is connected to
a small netbook pc with onboard
controller software.
Actuators
At each wheel corner there are three
robotic actuators attached. The wheel
motors are brushed DC motors with
planetary gearboxes. The speed
controllers consist of two dual motor
drivers with regenerative braking
ability.
Wheels and tyres
The tyre is filled with foam rubber
which gives the tyre different
stiffness in different directions.
One set of wheels chosen is a tyre
with a cord moulded into the tyre
carcass. This will give the possibility
to fill the tyre with pressurized air
instead of foam giving a more
realistic tyre design, with more
realistic behaviour as a consequence.
Sensors
The installed sensors have been
selected to give a sufficient level of
reliable
measurements
and
estimations of the vehicle's states.
Wheel speed
Internal Measuring Unit
PARAMETER ESTIMATION
By sensing force using the
actuators, wheel characteristics
can be measured on-board.
Cornering stiffness can be given
by measuring the force via the
actuators. The slip angle will be Actuators
calculated using the IMU signals. Wheel motors (brushed dc .05
One method is to use steady state with planetary gearbox)
~1000 rpm
cornering and measure the Speed
4.2 Nm
acceleration, speed and steering Max torque
15:1
angles, thus estimating wheel side Gear ratio
force as a function of wheel slip- Sensors
angles.
Wheel speed sensors (optical)
Video Online “Hjulia”
www.youtube.com/watch?v=RzQsRhNmKc
Actuators (steering/ride/camber) AX12
Speed
0.196 s/60 deg
Max torque
1.6 Nm
Gear ratio
254:1
Vehicle Data
Mass
ω1, ω2, ω3, ω4
~10 kg
Wheel base 450 mm
IMU (internal measurement unit) yaw rate, x-acceleration, y-acceleration
Width
250 mm
Actuator forces/positions
Cornering force, tyre load
Height
140 mm
Wheel motor current sensors
Used for estimating wheel torques
Wheel size Ø 100 mm
CONCLUSION
This poster presents a down-scaled
vehicle with ACM functionality that is
capable of controlling wheel torque,
steering, camber as well as wheel load
individually. The long-term aim of
the project is to improve drivability
and safety in hybrid electric vehicles,
by developing solutions for vehicle
motion control that utilize the
benefits
of
electro-mechanical
actuators. This vehicle will be a
valuable research platform for
evaluation
of
over-actuation
strategies, and the effect of non-ideal
sensors and actuators for control of
vehicle motion in real time.
ACKNOWLEDGEMENT
This work is financed by SHC, the Swedish Hybrid Vehicle Centre. It is one of the work-packages in the project “Generic
vehicle motion modelling and control for enhanced driving dynamics and energy management”. I would like to thank my
supervisors Annika Stensson Trigell, Lars Drugge and Jenny Jerrelind at KTH Vehicle Dynamics, and Mats Jonasson at
Volvo Car Corporation. I also want to thank Kent Lindgren and Danilo Prelevic at MWL for help with the prototype.
SHC
Swedish Hybrid
Vehicle Centre