Help with hovercar suspension

Help and Feedback Scripting Support
#1

Hello, I’m currently struggling attempting to find a solution to make my hovercar suspension more stable.
Currently, even a slight nudge will cause the vehicle to move quickly into the abyss. I would appreciate any help proposed solution this issue.

A demonstraction:
https://gyazo.com/a486231d6d27598e8440eaa05458c45e

As you can see, the suspension tries to correct the orientation, but to of no success.

Here is the module responsible for the physics component of my hovercar class:

-- physics
-- UntitledProtocol
-- November 29, 2020



local physics = {}
local mt = {__index = physics}

local function make_force(force_name, parent_instance)
    local attachement = Instance.new("Attachment")
    attachement.Orientation = Vector3.new(0,0,0)
    attachement.Position = parent_instance.Position
    attachement.Parent = parent_instance

    local force = Instance.new(force_name)
    force.Force = Vector3.new(0, 0, 0)
    force.Attachment0 = attachement
    force.ApplyAtCenterOfMass = true
    force.RelativeTo = Enum.ActuatorRelativeTo.Attachment0
    force.Parent = parent_instance

    return force
end

function physics.create(model, props)
    local self = setmetatable({}, mt)
    self.__model = model
    self.__props = props


    self.__contractions = {}

    -- Set up some constants for the suspension:
    local individual_mass = self.__model.com:GetMass() / #self.__model.suspension_points:GetChildren() -- mass divided by amount of suspension_points

    self.__spring_constant = individual_mass * workspace.Gravity + self.__props.spring_constant
    self.__damping_coefficient = 2 * (individual_mass * self.__spring_constant) ^ 0.5 -- find damping coefficient (critical damping) : 2 * sqrt(springConst * mass)

    -- Create a force for each of the suspensionPoints
    self.__suspension_forces = {}
    for _, v in ipairs(model.suspension_points:GetChildren()) do
        self.__suspension_forces[v] = make_force("VectorForce", v)
    end

    return self
end

function physics:__update(delta)
    self:__handle_suspension(delta)
end

function physics:__handle_suspension(delta)
    for part, force_object in pairs(self.__suspension_forces) do
        -- find how much the suspension has contracted:
        local was_grounded, height_from_ground = self:__get_height_off_ground(part)

        if not was_grounded then
            force_object.Force = Vector3.new(0,0,0)
            return
        end

        local contraction = self.__props.suspension_height - height_from_ground

        if not self.__contractions[part] then
            self.__contractions[part] = contraction
        end

        -- calculate derivative:
        local dx = (contraction - self.__contractions[part]) / delta
        self.__contractions[part] = contraction

        -- find force:
        local f = self.__spring_constant * contraction + dx * self.__damping_coefficient

        -- apply:
        force_object.Force = Vector3.new(0, f, 0)
    end
end

function physics:__get_height_off_ground(part)
    if not self.__raycast_params then
        local p  = RaycastParams.new()
        p.FilterDescendantsInstances = {self.__model}
        p.FilterType = Enum.RaycastFilterType.Blacklist
        self.__raycast_params = p
    end

    local origin_cf = part.CFrame * CFrame.new(0, -part.size.Y / 2, 0)
    local destination_cf = origin_cf * CFrame.new(0, -self.__props.suspension_height, 0)
    local direction = destination_cf.Position - origin_cf.Position

    local raycast_result = workspace:Raycast(origin_cf.Position, direction, self.__raycast_params)

    if raycast_result then
        return true, (origin_cf.Position - raycast_result.Position).Magnitude
    end
end

return physics
#2

You could probably try doubling the contraction value in physics:__handle_suspension(). In your example, I see that the hover wheels (idk what to call them lol) aren’t pushing up enough. Maybe this could help by pushing harder than normal, although this may cause the vehicle to be more unstable, but I guess you can multiply it by something in between 1-2.

#3

They are indeed pushing up. It is just that I set the maximum hover height to be 2 studs. Multiplying the contraction value would not make sense as it would mess up the equation.