The problem
Narrow vehicles save road space and energy in cities, but a narrow, tall vehicle can roll over in a turn. Tilting into the turn, like a motorcycle, solves this but needs a mechanism, an actuator or rider skill, and a lock for low speed. There is research interest in how to design such mechanisms for Indian urban mobility. This project builds the mechanical and kinematic basis for that work.
Objectives
- Define vehicle geometry, mass, tilt range and operating envelope.
- Design a parallelogram tilting front axle with an actuator and a tilt lock.
- Use Motion studies to find required tilt angle, actuator torque and tilt rate across manoeuvres.
- Compare passive, active and locked tilt strategies for stability and actuator demand.
- Check linkage strength and propose validation experiments.
What you need
Tools and toolboxes
- SOLIDWORKS Part and Assembly — Chassis, upper and lower tilt arms, uprights, wheels, steering and actuator with mates.
- SOLIDWORKS Motion Study (Motion Analysis) — Tilt actuator motors with expression or data-driven profiles, gravity and lateral acceleration as forces, plots of tilt angle, actuator torque and reactions; needs SOLIDWORKS Premium or a Simulation Professional or Premium licence.
- SOLIDWORKS Simulation (Static and Fatigue) — Tilt arms and pivots under combined vertical, lateral and actuator loads; fatigue needs Simulation Professional or Premium.
- Mass Properties — CG height and inertia of the vehicle with rider for the tilt dynamics.
- MATLAB or Excel — Steady-state tilt equation, simple tilt dynamics model and stability comparisons.
Software
- SOLIDWORKS 2023 or later (Premium for Motion Analysis)
- SOLIDWORKS Simulation
- MATLAB or Excel
Extra parts and data
- Measured rider and payload data — CG height of the vehicle with rider is the key input for tilt and rollover calculations.
Key concepts
- Steady-state tilt angle
- For a balanced turn, tan θ = v²/(g·R). The vehicle tilts so the resultant of gravity and centripetal force passes through the contact line.
- Parallelogram tilt linkage
- Upper and lower arms pivot on the chassis and the uprights, keeping the wheels parallel to the body as it tilts.
- Active versus passive tilt
- In active tilt an actuator sets the angle from sensed speed and steering; in passive tilt the rider balances like a motorcycle and the mechanism is free.
- Static rollover threshold
- For a non-tilting vehicle, the lateral acceleration at which it tips is about half the track divided by CG height. Tilt raises the effective threshold.
Step-by-step guide
- 1
Define the vehicle and envelope
Use an example narrow three-wheeler with two front wheels and one rear: front track 0.8 m, wheelbase 1.9 m, mass with rider 280 kg and CG height 0.6 m, stated as examples. Define a tilt range of ±30 degrees, an operating envelope of speeds up to 60 km/h and turn radii down to a city intersection, and a low-speed tilt lock below a stated speed. Write research questions comparing tilt strategies.
Checkpoint: A specification and research questions with stated example values.
- 2
Compute tilt requirements
In MATLAB or Excel, compute the steady-state tilt angle for each speed and turn radius in the envelope, and the rollover threshold of the non-tilting vehicle. Mark where tilt is needed to avoid rollover and where it exceeds the ±30 degree range. Estimate tilt rate for an example lane change from the tilt angle change and time. These results set the mechanism range and actuator speed.
Checkpoint: Maps of required tilt angle and rollover margin over speed and turn radius, and an estimated tilt rate.
- 3
Lay out the linkage
In a front-view layout sketch, draw the chassis pivots, upper and lower arms, uprights and wheels. Make each a block and drag through ±30 degrees of tilt. Check wheel contact patches stay on the ground line and that wheel camber equals body tilt. Check ground clearance of the arms at full tilt. Choose arm lengths and pivot spacing that keep loads reasonable.
Checkpoint: A layout that tilts through the full range with both contact patches on the ground.
- 4
Model the mechanism
Model upper and lower arms, uprights with kingpins, wheels and a chassis section. Add a tilt actuator, for example an electric motor with a gearbox driving the upper arm, and a tilt lock such as a disc brake or pin on the arm pivot. Add the steering connection so the front wheels steer while tilting. Assign materials and record Mass Properties of the full vehicle with rider mass.
Checkpoint: A full assembly whose CG and inertia match the specification within a small tolerance.
- 5
Assemble and check kinematics
Mate pivots with concentric mates and contact patches with the ground plane using a coincident or path-type constraint suitable for the analysis. Add a rotary motor at the tilt pivot and run a Basic Motion or Motion Analysis study through full tilt. Plot wheel camber, track change and contact patch positions. Check steering still works at full tilt with Interference Detection at the extremes.
Checkpoint: Kinematic plots confirming camber equals tilt and no interference at full tilt and lock.
- 6
Simulate steady turns
In Motion Analysis, apply gravity and a lateral force at the CG equal to m·v²/R for a chosen speed and radius. For active tilt, drive the tilt to the steady-state angle and plot actuator torque. For locked tilt, keep the mechanism fixed and plot wheel vertical reactions to see how close the inner wheel comes to lifting. For passive tilt, free the joint and note the torque needed to hold the angle.
Checkpoint: Actuator torque at steady turns for active tilt and inner-wheel load margin for locked tilt across the envelope.
- 7
Simulate transient manoeuvres
Use time-varying lateral force and tilt profiles from MATLAB for a lane change and a turn entry. Feed them into the Motion study through data-point or expression-driven motors and forces. Plot actuator torque, power and tilt error. Compare active tilt with a limited actuator against the ideal. Note that a full vehicle dynamics model with tyres is beyond this motion study.
Checkpoint: Transient torque and power curves, and the peak actuator demand for each manoeuvre.
- 8
Compare strategies
Tabulate for passive, active and locked tilt: rollover margin, actuator peak and RMS torque, energy per manoeuvre, rider effort and low-speed behaviour. Discuss practical issues: passive tilt needs rider skill and a lock at low speed, active tilt needs sensors and fault handling, locked tilt limits cornering speed. Use the results to recommend a strategy or hybrid for urban use.
Checkpoint: A strategy comparison table with a justified recommendation.
- 9
Check strength and fatigue
Export joint reactions from the worst manoeuvre and import into a static study of the arms and pivots, or apply manually. Refine mesh at pivot bosses and check factor of safety. If you have Simulation Professional or Premium, run a fatigue study with a repeated turn load cycle and a material S-N curve. Otherwise, use a hand fatigue check with an endurance limit.
Checkpoint: Factor of safety above an example 2 and a fatigue life estimate above a stated target.
- 10
Plan validation
Design a scale or full-size test rig: a tilting front-end mock-up on a frame with an actuator, load cells at pivots and an inclinometer. Define test cases matching simulated steady turns and transients. Set acceptance criteria, for example actuator torque within 15 per cent of prediction. List safety measures for any ridden prototype, including outriggers. State how test data will be compared with the simulation, using the same load cases and plots.
Checkpoint: A rig drawing, sensor list, test cases and acceptance criteria.
- 11
Write the research report
Present specification, tilt requirement maps, linkage design, kinematics, steady and transient results, strategy comparison, strength checks and validation plan. State limits clearly: rigid tyres, no full vehicle dynamics, assumed rider behaviour. Separate design rules supported by results from open questions for future work. Include the inputs and scripts needed to reproduce every plot. Discuss how the recommended strategy would change for a different CG height or track width, since these drive rollover margin. Propose the next study, such as a tyre-based vehicle dynamics model or a ridden prototype with outriggers.
Checkpoint: A report or paper draft with clear contributions, limits and next steps.
Testing & validation
- Layout and motion kinematics agree on camber and track through tilt.
- Steady-turn actuator torque matches a hand calculation of the tilt moment.
- Strength and fatigue checks meet targets at converged mesh.
- A physical validation rig is defined with acceptance criteria.
Expected results
A parallelogram tilting front-end design with tilt requirement maps, kinematic checks, actuator torque and power for steady and transient manoeuvres, a strategy comparison and strength-checked arms with a validation plan.
Research angle for your PhD
Narrow tilting vehicles suit dense Indian cities, but design rules for their mechanisms and actuators are not widely published. A study can map tilt requirements across Indian urban speeds and turn radii, compare passive, active and hybrid tilt on actuator demand, energy and safety, and validate actuator torque on a rig. The contribution is a design method and validated actuator sizing rules.
Take it further
- Build a vehicle dynamics model with tyres in MATLAB and couple it with the CAD-derived parameters.
- Design a hydraulic or spring-assisted tilt lock.
- Study fault cases such as actuator failure at full tilt.
- Build and test the scale rig and compare with simulation.
Viva and review questions
How do you calculate the needed tilt angle?
For a balanced steady turn, tan θ = v²/(g·R), so the angle depends on speed squared over turn radius.
Why lock tilt at low speed?
At low speed there is little centripetal force to balance, so a free tilting vehicle would fall over. A lock keeps it upright when stopped or manoeuvring slowly.
What does the parallelogram linkage do?
It keeps the front wheels parallel to the body as it tilts, so wheel camber equals body tilt and the contact patches stay on the ground.
What are the limits of your Motion study?
It uses rigid parts, applied lateral forces and no tyre model, so it gives actuator loads and kinematics but not full vehicle handling.
Learn it at DIYguru
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