$explorerprocesses = @(Get-WmiObject -Query "Select * FROM Win32_Process WHERE Name='explorer.exe'" -ErrorAction SilentlyContinue)
if ($explorerprocesses.Count -eq 0)
{
    "No explorer process found / Nobody interactively logged on"
} else {
    foreach ($i in $explorerprocesses)
    {
        $Username = $i.GetOwner().User
        $Domain = $i.GetOwner().Domain
        $Domain + "" + $Username + " logged on since: " + ($i.ConvertToDateTime($i.CreationDate))
    }
}

function get-logedonuser {
param (
 [string]$computername = $env:COMPUTERNAME
)
Get-WmiObject -Class Win32_LogonSession -ComputerName $computername |
foreach {
 $data = $_

 $id = $data.__RELPATH -replace """", "'"
 $q = "ASSOCIATORS OF {$id} WHERE ResultClass = Win32_Account"
 Get-WmiObject -ComputerName $computername -Query $q |
 select @{N="User";E={$($_.Caption)}},
 @{N="LogonTime";E={$data.ConvertToDateTime($data.StartTime)}}
}
}